OLED device with certain fluoranthene light-emitting dopants

ABSTRACT

An OLED device comprising a cathode, an anode, and having therebetween a light emitting layer and an electron-injecting layer, where (a) the light emitting layer contains a host and up to 50 volume % of a light-emitting fluoranthene compound with a 7,10-diaryl substituted fluoranthene nucleus having no aromatic rings annulated to the fluoranthene nucleus; and (b) the electron-injecting layer being located between the cathode and the light-emitting layer contains an organic alkali metal compound. It provides reduced drive voltage, operational stability and luminance of OLED devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

Reference is made to the following five cases, including this one, thatwere cofiled:

-   U.S. Patent Application Publication No. 2009/0108735 entitled OLED    DEVICE WITH FLUORANTHENE ELECTRON TRANSPORT MATERIALS;-   U.S. Patent Application Publication No. 2009/0110957 entitled OLED    DEVICE WITH CERTAIN FLUORANTHENE HOST;-   U.S. Patent Application Publication No. 2009/0110956 entitled OLED    DEVICE WITH ELECTRON TRANSPORT MATERIAL COMBINATION; and-   U.S. Patent Application Publication No. 2009/0108736 entitled    PHOSPHORESCENT OLED DEVICE WITH CERTAIN FLUORANTHENE HOST.

FIELD OF THE INVENTION

This invention relates to an organic light-emitting diode (OLED)electroluminescent (EL) device having a light-emitting layer including ahost material and a specific type of fluoranthene light-emitting dopant,and an electron injection layer including an organic lithium material.

BACKGROUND OF THE INVENTION

While organic electroluminescent (EL) devices have been known for overtwo decades, their performance limitations have represented a barrier tomany desirable applications. In simplest form, an organic EL device iscomprised of an anode for hole injection, a cathode for electroninjection, and an organic medium sandwiched between these electrodes tosupport charge recombination that yields emission of light. Thesedevices are also commonly referred to as organic light-emitting diodes,or OLEDs. Representative of earlier organic EL devices are Gurnee et al.U.S. Pat. No. 3,172,862, issued Mar. 9, 1965; Gurnee U.S. Pat. No.3,173,050, issued Mar. 9, 1965; Dresner, “Double InjectionElectroluminescence in Anthracene”, RCA Review, 30, 322, (1969); andDresner U.S. Pat. No. 3,710,167, issued Jan. 9, 1973. The organic layersin these devices, usually composed of a polycyclic aromatic hydrocarbon,were very thick (much greater than 1 μm). Consequently, operatingvoltages were very high, often greater than 100V.

More recent organic EL devices include an organic EL element consistingof extremely thin layers (e.g. <1.0 μm) between the anode and thecathode. Herein, the term “organic EL element” encompasses the layersbetween the anode and cathode. Reducing the thickness lowered theresistance of the organic layers and has enabled devices that operate atmuch lower voltage. In a basic two-layer EL device structure, describedfirst in U.S. Pat. No. 4,356,429, one organic layer of the EL elementadjacent to the anode is specifically chosen to transport holes, andtherefore is referred to as the hole-transporting layer, and the otherorganic layer is specifically chosen to transport electrons and isreferred to as the electron-transporting layer. Recombination of theinjected holes and electrons within the organic EL element results inefficient electroluminescence.

There have also been proposed three-layer organic EL devices thatcontain an organic light-emitting layer (LEL) between thehole-transporting layer and electron-transporting layer, such as thatdisclosed by C. Tang et al. (J. Applied Physics, Vol. 65, 3610 (1989)).The light-emitting layer commonly consists of a host material doped witha guest material, otherwise known as a dopant. Still further, there hasbeen proposed in U.S. Pat. No. 4,769,292 a four-layer EL elementcomprising a hole injecting layer (HIL), a hole-transporting layer(HTL), a light-emitting layer (LEL) and anelectron-transporting/injecting layer (ETL). These structures haveresulted in improved device efficiency.

EL devices in recent years have expanded to include not only singlecolor emitting devices, such as red, green and blue, but alsowhite-devices, devices that emit white light. Efficient white lightproducing OLED devices are highly desirable in the industry and areconsidered as a low cost alternative for several applications such aspaper-thin light sources, backlights in LCD displays, automotive domelights, and office lighting. White light producing OLED devices shouldbe bright, efficient, and generally have Commission Internationald'Eclairage (CIE) chromaticity coordinates of about (0.33, 0.33). In anyevent, in accordance with this disclosure, white light is that lightwhich is perceived by a user as having a white color.

Since the early inventions, further improvements in device materialshave resulted in improved performance in attributes such as color,stability, luminance efficiency and manufacturability, e.g., asdisclosed in U.S. Pat. No. 5,061,569, U.S. Pat. No. 5,409,783, U.S. Pat.No. 5,554,450, U.S. Pat. No. 5,593,788, U.S. Pat. No. 5,683,823, U.S.Pat. No. 5,908,581, U.S. Pat. No. 5,928,802, U.S. Pat. No. 6,020,078,and U.S. Pat. No. 6,208,077, amongst others.

Notwithstanding all of these developments, there are continuing needsfor organic EL device components, such as blue light-emitting dopantsand/or electron injecting materials, that will provide even lower devicedrive voltages and hence lower power consumption, while maintaining highluminance efficiencies and long lifetimes combined with high colorpurity.

A useful class of electron-transporting materials is that derived frommetal chelated oxinoid compounds including chelates of oxine itself,also commonly referred to as 8-quinolinol or 8-hydroxyquinoline.Tris(8-quinolinolato)aluminum (III), also known as Alq or Alq3, andother metal and non-metal oxine chelates are well known in the art aselectron-transporting materials. Tang et al., in U.S. Pat. No. 4,769,292and VanSlyke et al., in U.S. Pat. No. 4,539,507 lower the drive voltageof the EL devices by teaching the use of Alq as an electron transportmaterial in the luminescent layer or luminescent zone. Baldo et al., inU.S. Pat. No. 6,097,147 and Hung et al., in U.S. Pat. No. 6,172,459teach the use of an organic electron-transporting layer adjacent to thecathode so that when electrons are injected from the cathode into theelectron-transporting layer, the electrons traverse both theelectron-transporting layer and the light-emitting layer.

Fluoranthene derivatives are well known in the art as being useful ashosts in light-emitting layers as well as other non-emissive layers suchas hole blocking layers or electron transporting layers. For example,see US20050271899A1, U.S. Pat. No. 6,613,454, US20020168544A1, U.S. Pat.No. 7,183,010B2, U.S. Pat. No. 7,175,922B2, US20060141287A1 andUS20070069198.

US 20020022151A1 describes the use of fluoranthenes with at least oneamino group directly substituted on the fluoranthene ring in lightemitting layers as well as hole and electron transporting layers.

EP1719748A2 describes the use of bis-benzofluoranthene derivatives inlight emitting layers, hole and electron transporting layers as well aselectron injecting layers.

US20060238110A1 and WO2007039344A2 describe the use of polymericfluoranthene derivatives as blue light-emitting dopants.

EP1718124A1 describes the use of certain fluoranthene derivatives asyellow-to-reddish light-emitting dopants.

WO2007039344A3 describes the use of fluoranthene derivatives as bluelight-emitting dopants. U.S. Pat. No. 6,803,120B2 describes the use offluorescent fluoranthenes in combination with a host and blue-lightemitting dopant.

The use of organic lithium compounds in an electron-injection layer ofan EL device is also known; for example, see US20060286405,US20020086180, US20040207318, U.S. Pat. No. 6,396,209, JP2000053957,WO9963023 and U.S. Pat. No. 6,468,676.

However, these devices do not have all desired EL characteristics interms of high luminance and stability of the components in combinationwith low drive voltages.

Notwithstanding all these developments, there remains a need to reducedrive voltage of OLED devices, as well as to provide embodiments withother improved features such as operational stability and luminance.

SUMMARY OF THE INVENTION

The invention provides an OLED device comprising a cathode, an anode,and having therebetween a light emitting layer and an electrontransporting layer,

(a) the light emitting layer containing a host and up to 50 volume % ofa light-emitting fluoranthene compound with a 7,10-diaryl substitutedfluoranthene nucleus having no aromatic rings annulated to thefluoranthene nucleus; and

(b) the electron transporting layer being located between the cathodeand the light-emitting layer containing an organic alkali metalcompound.

In another embodiment, the OLED device also includes anelectron-transporting layer comprising a fluoranthene compound with a7,10-diaryl substituted fluoranthene nucleus having no aromatic ringsannulated to the fluoranthene nucleus.

Devices of the invention provide reduced drive voltage of OLED devices,and provide embodiments with other improved features such as operationalstability and high luminance

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic cross-sectional view of one embodiment of theOLED device of the present invention. It will be understood that FIG. 1is not to scale since the individual layers are too thin and thethickness differences of various layers are too great to permitdepiction to scale.

DETAILED DESCRIPTION OF THE INVENTION

The invention is generally as described above. An OLED device of theinvention is a multilayer electroluminescent device comprising acathode, an anode, light-emitting layer(s) (LEL), electron-transportinglayer(s) (ETL) and electron-injecting layer(s) (EIL) and optionallyadditional layers such as hole-injecting layer(s), hole-transportinglayer(s), exciton-blocking layer(s), spacer layer(s), connectinglayer(s) and hole-blocking layer(s).

The LEL of the invention includes a host material and a certain type offluoranthene compound that serves as a light-emitting dopant. There maybe one or more host materials present that in total comprise 50% or moreof the total volume of all of the materials in the LEL. The fluoranthenematerial emits light when a potential is applied to the LEL and ispresent at less than 50% by volume. There may be additionallight-emitting materials that emit the same or different colors of lightin the LEL in addition to the fluoranthene.

The fluoranthene compounds of the invention are those other than oneswhere the fluoranthene nucleus contains annulated rings. They arehydrocarbons and contain no heteroatoms as part of the ring system ofthe nucleus. The fluoranthene nucleus contains only 4 annulated ringswhose numbering sequence is shown below:

The fluoranthenes of the invention contain no additional annulated ringsto the above nucleus. Annulated rings are those rings that share acommon ring bond between any two carbon atoms of the fluoranthenenucleus.

Suitably, the 7,10-diaryl-fluoranthene compounds of the invention areaccording to Formula (I):

wherein:

each Ar is an aromatic ring containing 6 to 24 carbon atoms and can bethe same or different; and

R₁-R₈ are individually selected from hydrogen and aromatic ringscontaining 6 to 24 carbon atoms with the proviso that no two adjacentR₁-R₈ substituents can join to form an annulated or fused aromatic ringsystem.

In formula (I), the Ar group(s) can be heterocyclic but preferred arecarbocyclic groups. The Ar group(s) cannot be fused with thefluoranthene nucleus and are connected only by one single bond.Preferred Ar groups are phenyl or napthyl with phenyl being particularlypreferred. Compounds where the Ar groups are the same are alsodesirable.

More preferred compounds of the invention are according to Formula (II):

wherein

R₁, R₂, R₃ and R₄ are independently hydrogen or an aromatic groupcontaining 6 to 24 carbon atoms with the proviso that any adjacent R₁-R₄is not part of an aromatic ring annulated to the nucleus;

R is hydrogen or a substituent; and

n and m are independently 1-5.

Most preferred fluoranthenes are according to Formula (III-a) or(III-b):

wherein:

R₂ and R₄ are independently hydrogen or an aromatic group containing 6to 24 carbon atoms with the proviso that R₂ and R₄ cannot both behydrogen nor can R₂ be joined with R to form a ring; and

R is hydrogen or a substituent; and

n and m are independently 1-5.

In Formulas (II) and (III), the most preferred R₁, R₂, R₃ and R₄ groupsare phenyl or napthyl, which may be further substituted. A particularlypreferred substituted phenyl group is biphenyl. Biphenyl can beortho(o), meta(m) or para(p) substituted biphenyl, with p-biphenyl beingparticularly preferred. Other aromatic ring systems such as anthracene,phenanthrene, phenanthroline and perylene are also suitable as thesesubstituents. Typically, the R substituent(s) are hydrogen but may beany suitable group chosen to modify the molecular properties. It is alsocontemplated that the fluoranthene of the invention can consist of morethan one separate fluoranthene nucleus; that is, two or morefluoranthene groups can be linked through a single bond so that they arenot annulated together.

However, the fluoranthene derivatives used in the invention are notpolymeric; do not have multiple fluoranthene groups covalently attachedto a polymeric backbone or where the fluoranthene nucleus is directlypart of the polymeric chain. The fluoranthenes of the invention aresmall molecules with molecular weights typically below 1500, preferablybelow 1000.

In addition, the fluoranthene compounds used in the invention cannothave any amino substituents attached directly to the fluoranthenenucleus. Thus, none of R₁-R₈ in Formula (I), (II) or (III) can be anamino group such as diarylamine. However, it is possible that thearomatic rings containing 6 to 24 carbon atoms of R₁-R₈ may be furthersubstituted with amino groups.

The fluoranthene compounds used in the invention cannot have additionalaromatic rings annulated to either the phenyl or napthyl rings of thefluoranthene nucleus ring system. Fluoranthenes with additionalannulated ring systems are not part of this invention. Four specificexamples of compounds containing a fluoranthene nucleus with annulatedring systems that are excluded are:

Specific examples of fluoranthene light-emitting materials of theinvention are as follows:

The invention additionally requires a layer, located between the cathodeand the electron-transporting layer, that contains an organic alkalimetal compound. This layer is typically referred to as anelectron-injection layer (EIL). Such layers are commonly locateddirectly adjacent to the cathode and assist in the efficient transfer ofelectrons towards the light-emitting layer. A common partial layer orderis LEL|ETL|EL|cathode. The ETL and EIL may be split into multiplesublayers. There may be intermediate layers between any of these 3interfaces; for example, a thin layer of LiF between the cathode and theEIL. The organic alkali metal compounds may also be present in the ETLas well as the EIL.

The EIL may be composed only of a single organic alkali metal compoundor may be a mixture of 2 or more organic alkali metal compounds. Inaddition to the alkali metal compounds, the EIL may also contain one ormore polycyclic aromatic hydrocarbons. The % volume ratio of organicalkali metal compound to additional material can be anywhere from 1% to99%, more suitably at least 10% and typically, at least 30%. Thethickness of the EIL can be 0.1 nm to 20 nm in thickness, but preferably0.4 nm to 10 nm, and more preferable from 1 nm to 8 nm.

The alkali metal used in the compounds of the invention belongs to Group1 of the periodic table. Of these, lithium is highly preferred.

Organic lithium compounds (electron injection material or EIM) useful inthe invention are according to Formula (IV):(Li⁺)_(m)(Q)_(n)  Formula (IV)wherein:

Q is an anionic organic ligand; and

m and n are independently selected integers selected to provide aneutral charge on the complex.

The anionic organic ligand Q is most suitably monoanionic and containsat least one ionizable site consisting of oxygen, nitrogen or carbon. Inthe case of enolates or other tautomeric systems containing oxygen, itwill be considered and drawn with the lithium bonded to the oxygenalthough the lithium may in fact can be bonded elsewhere to form achelate. It is also desirable that the ligand contains at least onenitrogen atom that can form a coordinate or dative bond with thelithium. The integers m and n can be greater than 1 reflecting a knownpropensity for some organic lithium compounds to form cluster complexes.

In another embodiment, Formula (V) represents the EIM.

wherein:

Z and the dashed arc represent two to four atoms and the bonds necessaryto complete a 5- to 7-membered ring with the lithium cation;

each A represents hydrogen or a substituent and each B representshydrogen or an independently selected substituent on the Z atoms,provided that two or more substituents may combine to form a fused ringor a fused ring system; and

j is 0-3 and k is 1 or 2; and

m and n are independently selected integers selected to provide aneutral charge on the complex.

Of compounds of Formula (V), it is most desirable that the A and Bsubstituents together form an additional ring system. This additionalring system may further contain additional heteroatoms to form amultidentate ligand with coordinate or dative bonding to the lithium.Desirable heteroatoms are nitrogen or oxygen.

In Formula (V), it is preferred that the oxygen shown is part of ahydroxyl, carboxy or keto group. Examples of suitable nitrogen ligandsare 8-hydroxyquinoline, 2-hydroxymethylpyridine, pipecolinic acid or2-pyridinecarboxylic acid.

Specific examples of electron injecting materials of the invention areas follows:

FIG. 1 shows one embodiment of the invention in which light-emittinglayers, electron-transporting and electron-injecting layers are present.The fluoranthene compound of the invention is located in thelight-emitting layer (LEL, 134). An optional hole-blocking layer (HBL,135) is shown between the light-emitting layer and theelectron-transporting layer. The FIGURE also shows an optionalhole-injecting layer (HIL, 130). In this embodiment, the organic lithiumcompound is contained in the electron-injecting layer (EIL, 138) andserves as the said additional layer. In another embodiment, there is nohole-blocking layer (HBL, 135) located between the ETL and the LEL. Inyet other embodiments, there may be more than one hole-injecting,electron-injecting and electron-transporting layers.

Examples of preferred combinations of the invention are those whereinthe fluoranthene compound is selected from ETM1, ETM2, ETM3, ETM6, ETM9and ETM11 and the organic lithium compound is selected from EIM1, EIM2and EIM3.

The fluoranthene derivatives of the invention most suitably emit bluelight and it is preferred that the LEL containing the host andfluoranthene emitting compound emits predominately blue light. However,other light-emitting materials may be present in the same LEL orlight-emitting zone and they may be fluorescent or phosphorescent. Whenanother light-emitting material is present in the same LEL, it ispreferred that it emits a colored light other than blue light. Therelative amount of any additional light-emitting material may beadjusted so that the entire LEL produces predominately blue light withsmaller amounts of light of another color, adjusted so that the LELproduces roughly equivalent of blue and other colors of light such toproduce a white light, or adjusted so that the amounts of the othercolors of light are greater than the blue light.

While the fluoranthene compound is present in the LEL at less than 50%by volume, it is preferred that it is present at less than 25% andgreater than 0.5% with the most desirable range being from 1% to 12%.

The LEL containing the fluoranthene must also contain at least one hostmaterial. Any material known to be a suitable host for a light-emittinglayer can be used. It may have hole-transporting properties,electron-transporting properties or possess the ability to do both. Inone embodiment, two hosts could be used; the first withelectron-transporting properties and the second with hole-transportingproperties. Hosts known for being useful with a fluorescent dopant (forexamples, see the discussion below concerning fluorescent LELs) arepreferred, particularly those with electron-transporting properties.Hosts derived from polycyclic aromatic hydrocarbons are particularlyuseful with those derived from anthracene being the most useful.

In another embodiment, the OLED device also includes anelectron-transporting layer comprising a 7,10-diaryl-fluoranthenecompound with no annulated aromatic rings and optionally, may contain anorganic lithium compound. The fluoranthene light-emitting materialsaccording to this invention have excellent electron-transportingproperties that makes them very suitable for use inelectron-transporting layers. Suitable fluoranthenes for use in an ETLare those according to Formulae (I), (II) and (III). In an ETL, they maybe the sole material present in the layer or may be mixed withadditional materials. In particular, it is desirable to include both thefluoranthenes and EIMs of this invention together in an ETL. SuitableEIMs for mixing in the ETL are those according to Formula (IV) or morepreferably, those according to Formula (V).

In one suitable embodiment the EL device includes a means for emittingwhite light, which may include complimentary emitters, a white emitter,or a filtering means. The device may also include combinations offluorescent emitting materials and phosphorescent emitting materials(sometimes referred to as hybrid OLED devices). To produce a whiteemitting device, ideally the hybrid fluorescent/phosphorescent devicewould comprise a blue fluorescent emitter and proper proportions of agreen and red phosphorescent emitter, or other color combinationssuitable to make white emission. However, hybrid devices havingnon-white emission may also be useful by themselves. Hybridfluorescent/phosphorescent elements having non-white emission may alsobe combined with additional phosphorescent elements in series in astacked OLED. For example, white emission may be produced by one or morehybrid blue fluorescent/red phosphorescent elements stacked in serieswith a green phosphorescent element using p/n junction connectors asdisclosed in Tang et al U.S. Pat. No. 6,936,961B2. This invention may beused in so-called stacked device architecture, for example, as taught inU.S. Pat. No. 5,703,436 and U.S. Pat. No. 6,337,492.

In one desirable embodiment the EL device is part of a display device.In another suitable embodiment the EL device is part of an area lightingdevice.

The EL device of the invention is useful in any device where stablelight emission is desired such as a lamp or a component in a static ormotion imaging device, such as a television, cell phone, DVD player, orcomputer monitor.

As used herein and throughout this application, the term carbocyclic andheterocyclic rings or groups are generally as defined by the Grant &Hackh's Chemical Dictionary, Fifth Edition, McGraw-Hill Book Company. Acarbocyclic ring is any aromatic or non-aromatic ring system containingonly carbon atoms and a heterocyclic ring is any aromatic ornon-aromatic ring system containing both carbon and non-carbon atomssuch as nitrogen (N), oxygen (O), sulfur (S), phosphorous (P), silicon(Si), gallium (Ga), boron (B), beryllium (Be), indium (In), aluminum(Al), and other elements found in the periodic table useful in formingring systems. For the purpose of this invention, also included in thedefinition of a heterocyclic ring are those rings that includecoordinate bonds. The definition of a coordinate or dative bond can befound in Grant & Hackh's Chemical Dictionary, pages 91 and 153. Inessence, a coordinate bond is formed when electron rich atoms such as Oor N, donate a pair of electrons to electron deficient atoms or ionssuch as aluminum, boron or alkali metal ions such as Li⁺, Na⁺, K⁺ andCs⁺. One such example is found in tris(8-quinolinolato)aluminum(III),also referred to as Alq, wherein the nitrogen on the quinoline moietydonates its lone pair of electrons to the aluminum atom thus forming theheterocycle and hence providing Alq with a total of 3 fused rings. Thedefinition of a ligand, including a multidentate ligand, can be found inGrant & Hackh's Chemical Dictionary, pages 337 and 176, respectively.

Unless otherwise specifically stated, use of the term “substituted” or“substituent” means any group or atom other than hydrogen. Additionally,when the term “group” is used, it means that when a substituent groupcontains a substitutable hydrogen, it is also intended to encompass notonly the substituents unsubstituted form, but also its form furthersubstituted with any substituent group or groups as herein mentioned, solong as the substituent does not destroy properties necessary for deviceutility. Suitably, a substituent group may be halogen or may be bondedto the remainder of the molecule by an atom of carbon, silicon, oxygen,nitrogen, phosphorous, sulfur, selenium, or boron. The substituent maybe, for example, halogen, such as chloro, bromo or fluoro; nitro;hydroxyl; cyano; carboxyl; or groups which may be further substituted,such as alkyl, including straight or branched chain or cyclic alkyl,such as methyl, trifluoromethyl, ethyl, t-butyl,3-(2,4-di-t-pentylphenoxy)propyl, and tetradecyl; alkenyl, such asethylene, 2-butene; alkoxy, such as methoxy, ethoxy, propoxy, butoxy,2-methoxyethoxy, sec-butoxy, hexyloxy, 2-ethylhexyloxy, tetradecyloxy,2-(2,4-di-t-pentylphenoxy)ethoxy, and 2-dodecyloxyethoxy; aryl such asphenyl, 4-t-butylphenyl, 2,4,6-trimethylphenyl, naphthyl; aryloxy, suchas phenoxy, 2-methylphenoxy, alpha- or beta-naphthyloxy, and 4-tolyloxy;carbonamido, such as acetamido, benzamido, butyramido, tetradecanamido,alpha-(2,4-di-t-pentyl-phenoxy)acetamido,alpha-(2,4-di-t-pentylphenoxy)butyramido,alpha-(3-pentadecylphenoxy)-hexanamido,alpha-(4-hydroxy-3-t-butylphenoxy)-tetradecanamido,2-oxo-pyrrolidin-1-yl, 2-oxo-5-tetradecylpyrrolin-1-yl,N-methyltetradecanamido, N-succinimido, N-phthalimido,2,5-dioxo-1-oxazolidinyl, 3-dodecyl-2,5-dioxo-1-imidazolyl, andN-acetyl-N-dodecylamino, ethoxycarbonylamino, phenoxycarbonylamino,benzyloxycarbonylamino, hexadecyloxycarbonylamino,2,4-di-t-butylphenoxycarbonylamino, phenylcarbonylamino,2,5-(di-t-pentylphenyl)carbonylamino, p-dodecyl-phenylcarbonylamino,p-tolylcarbonylamino, N-methylureido, N,N-dimethylureido,N-methyl-N-dodecylureido, N-hexadecylureido, N,N-dioctadecylureido,N,N-dioctyl-N′-ethylureido, N-phenylureido, N,N-diphenylureido,N-phenyl-N-p-tolylureido, N-(m-hexadecylphenyl)ureido,N,N-(2,5-di-t-pentylphenyl)-N′-ethylureido, and t-butylcarbonamido;sulfonamido, such as methylsulfonamido, benzenesulfonamido,p-tolylsulfonamido, p-dodecylbenzenesulfonamido,N-methyltetradecylsulfonamido, N,N-dipropyl-sulfamoylamino, andhexadecylsulfonamido; sulfamoyl, such as N-methylsulfamoyl,N-ethylsulfamoyl, N,N-dipropylsulfamoyl, N-hexadecylsulfamoyl,N,N-dimethylsulfamoyl, N-[3-(dodecyloxy)propyl]sulfamoyl,N-[4-(2,4-di-t-pentylphenoxy)butyl]sulfamoyl,N-methyl-N-tetradecylsulfamoyl, and N-dodecylsulfamoyl; carbamoyl, suchas N-methylcarbamoyl, N,N-dibutylcarbamoyl, N-octadecylcarbamoyl,N-[4-(2,4-di-t-pentylphenoxy)butyl]carbamoyl,N-methyl-N-tetradecylcarbamoyl, and N,N-dioctylcarbamoyl; acyl, such asacetyl, (2,4-di-t-amylphenoxy)acetyl, phenoxycarbonyl,p-dodecyloxyphenoxycarbonyl methoxycarbonyl, butoxycarbonyl,tetradecyloxycarbonyl, ethoxycarbonyl, benzyloxycarbonyl,3-pentadecyloxycarbonyl, and dodecyloxycarbonyl; sulfonyl, such asmethoxysulfonyl, octyloxysulfonyl, tetradecyloxysulfonyl,2-ethylhexyloxysulfonyl, phenoxysulfonyl,2,4-di-t-pentylphenoxysulfonyl, methylsulfonyl, octylsulfonyl,2-ethylhexylsulfonyl, dodecylsulfonyl, hexadecylsulfonyl,phenylsulfonyl, 4-nonylphenylsulfonyl, and p-tolylsulfonyl; sulfonyloxy,such as dodecylsulfonyloxy, and hexadecylsulfonyloxy; sulfinyl, such asmethylsulfinyl, octylsulfinyl, 2-ethylhexylsulfinyl, dodecylsulfinyl,hexadecylsulfinyl, phenylsulfinyl, 4-nonylphenylsulfinyl, andp-tolylsulfinyl; thio, such as ethylthio, octylthio, benzylthio,tetradecylthio, 2-(2,4-di-t-pentylphenoxy)ethylthio, phenylthio,2-butoxy-5-t-octylphenylthio, and p-tolylthio; acyloxy, such asacetyloxy, benzoyloxy, octadecanoyloxy, p-dodecylamidobenzoyloxy,N-phenylcarbamoyloxy, N-ethylcarbamoyloxy, and cyclohexylcarbonyloxy;amine, such as phenylanilino, 2-chloroanilino, diethylamine,dodecylamine; imino, such as 1 (N-phenylimido)ethyl, N-succinimido or3-benzylhydantoinyl; phosphate, such as dimethylphosphate andethylbutylphosphate; phosphite, such as diethyl and dihexylphosphite; aheterocyclic group, a heterocyclic oxy group or a heterocyclic thiogroup, each of which may be substituted and which contain a 3 to 7membered heterocyclic ring composed of carbon atoms and at least onehetero atom selected from the group consisting of oxygen, nitrogen,sulfur, phosphorous, or boron. Such as 2-furyl, 2-thienyl,2-benzimidazolyloxy or 2-benzothiazolyl; quaternary ammonium, such astriethylammonium; quaternary phosphonium, such as triphenylphosphonium;and silyloxy, such as trimethylsilyloxy.

If desired, the substituents may themselves be further substituted oneor more times with the described substituent groups. The particularsubstituents used may be selected by those skilled in the art to attaindesirable properties for a specific application and can include, forexample, electron-withdrawing groups, electron-donating groups, andsteric groups. When a molecule may have two or more substituents, thesubstituents may be joined together to form a ring such as a fused ringunless otherwise provided. Generally, the above groups and substituentsthereof may include those having up to 48 carbon atoms, typically 1 to36 carbon atoms and usually less than 24 carbon atoms, but greaternumbers are possible depending on the particular substituents selected.

The following is the description of the layer structure, materialselection, and fabrication process for OLED devices.

General OLED Device Architecture

The present invention can be employed in many OLED configurations usingsmall molecule materials, oligomeric materials, polymeric materials, orcombinations thereof. These include from very simple structures having asingle anode and cathode to more complex devices, such as passive matrixdisplays having orthogonal arrays of anodes and cathodes to form pixels,and active-matrix displays where each pixel is controlled independently,for example, with thin film transistors (TFTs). There are numerousconfigurations of the organic layers wherein the present invention issuccessfully practiced. For this invention, essential requirements are acathode, an anode, a LEL, an ETL and a HIL.

One embodiment according to the present invention and especially usefulfor a small molecule device is shown in FIG. 1. OLED 100 contains asubstrate 110, an anode 120, a hole-injecting layer 130, ahole-transporting layer 132, a light-emitting layer 134, a hole-blockinglayer 135, an electron-transporting layer 136, an electron-injectinglayer 138 and a cathode 140. In some other embodiments, there areoptional spacer layers on either side of the LEL. These spacer layers donot typically contain light emissive materials. All of these layer typeswill be described in detail below. Note that the substrate mayalternatively be located adjacent to the cathode, or the substrate mayactually constitute the anode or cathode. Also, the total combinedthickness of the organic layers is preferably less than 500 nm.

The anode and cathode of the OLED are connected to a voltage/currentsource 150, through electrical conductors 160. Applying a potentialbetween the anode and cathode such that the anode is at a more positivepotential than the cathode operates the OLED. Holes are injected intothe organic EL element from the anode. Enhanced device stability cansometimes be achieved when the OLED is operated in an AC mode where, forsome time period in cycle, the potential bias is reversed and no currentflows. An example of an AC driven OLED is described in U.S. Pat. No.5,552,678.

Anode

When the desired EL emission is viewed through the anode, anode 120should be transparent or substantially transparent to the emission ofinterest. Common transparent anode materials used in this invention areindium-tin oxide (ITO), indium-zinc oxide (IZO) and tin oxide, but othermetal oxides can work including, but not limited to, aluminum- orindium-doped zinc oxide, magnesium-indium oxide, and nickel-tungstenoxide. In addition to these oxides, metal nitrides, such as galliumnitride, and metal selenides, such as zinc selenide, and metal sulfides,such as zinc sulfide, can be used as the anode 120. For applicationswhere EL emission is viewed only through the cathode 140, thetransmissive characteristics of the anode 120 are immaterial and anyconductive material can be used, transparent, opaque or reflective.Example conductors for this application include, but are not limited to,gold, iridium, molybdenum, palladium, and platinum. Typical anodematerials, transmissive or otherwise, have a work function of 4.1 eV orgreater. Desired anode materials are commonly deposited by any suitablemeans such as evaporation, sputtering, chemical vapor deposition, orelectrochemical means. Anodes can be patterned using well-knownphotolithographic processes. Optionally, anodes may be polished prior toapplication of other layers to reduce surface roughness so as tominimize short circuits or enhance reflectivity.

Hole Injection Layer

Although it is not always necessary, it is often useful to provide anHIL in the OLEDs. HIL 130 in the OLEDs can serve to facilitate holeinjection from the anode into the HTL, thereby reducing the drivevoltage of the OLEDs. Suitable materials for use in HIL 130 include, butare not limited to, porphyrinic compounds as described in U.S. Pat. No.4,720,432 and some aromatic amines, for example,4,4′,4″-tris[(3-ethylphenyl)phenylamino]triphenylamine (m-TDATA).Alternative hole-injecting materials reportedly useful in OLEDs aredescribed in EP 0 891 121 A1 and EP 1 029 909 A1. Aromatic tertiaryamines discussed below can also be useful as hole-injecting materials.Other useful hole-injecting materials such asdipyrazino[2,3-f:2′,3′-h]quinoxalinehexacarbonitrile are described inU.S. Patent Application Publication 2004/0113547 A1 and U.S. Pat. No.6,720,573. In addition, a p-type doped organic layer is also useful forthe HIL as described in U.S. Pat. No. 6,423,429. The term “p-type dopedorganic layer” means that this layer has semiconducting properties afterdoping, and the electrical current through this layer is substantiallycarried by the holes. The conductivity is provided by the formation of acharge-transfer complex as a result of hole transfer from the dopant tothe host material.

The thickness of the HIL 130 is in the range of from 0.1 nm to 200 nm,preferably, in the range of from 0.5 m to 150 nm.

Hole Transport Layer

The HTL 132 contains at least one hole-transporting material such as anaromatic tertiary amine, where the latter is understood to be a compoundcontaining at least one trivalent nitrogen atom that is bonded only tocarbon atoms, at least one of which is a member of an aromatic ring. Inone form the aromatic tertiary amine is an arylamine, such as amonoarylamine, diarylamine, triarylamine, or a polymeric arylamine.Exemplary monomeric triarylamines are illustrated by Klupfel et al. U.S.Pat. No. 3,180,730. Other suitable triarylamines substituted with one ormore vinyl radicals or at least one active hydrogen-containing group aredisclosed by Brantley, et al. in U.S. Pat. Nos. 3,567,450 and 3,658,520.

A more preferred class of aromatic tertiary amines are those whichinclude at least two aromatic tertiary amine moieties as described inU.S. Pat. Nos. 4,720,432 and 5,061,569. Such compounds include thoserepresented by structural Formula (A)

wherein:

Q₁ and Q₂ are independently selected aromatic tertiary amine moieties;and

G is a linking group such as an arylene, cycloalkylene, or allylenegroup of a carbon to carbon bond.

In one embodiment, at least one of Q₁ or Q₂ contains a polycyclic fusedring structure, e.g., a naphthalene. When G is an aryl group, it isconveniently a phenylene, biphenylene, or naphthalene moiety.

A useful class of triarylamines satisfying structural Formula A andcontaining two triarylamine moieties is represented by structuralFormula (B)

wherein:

R₁ and R₂ each independently represents a hydrogen atom, an aryl group,or an alkyl group or R₁ and R₂ together represent the atoms completing acycloalkyl group; and

R₃ and R₄ each independently represents an aryl group, which is in turnsubstituted with a diaryl substituted amino group, as indicated bystructural Formula (C)

wherein:

R₅ and R₆ are independently selected aryl groups. In one embodiment, atleast one of R₅ or R₆ contains a polycyclic fused ring structure, e.g.,a naphthalene.

Another class of aromatic tertiary amines are the tetraaryldiamines.Desirable tetraaryldiamines include two diarylamino groups, such asindicated by Formula (C), linked through an arylene group. Usefultetraaryldiamines include those represented by Formula (D)

wherein:

each ARE is an independently selected arylene group, such as a phenyleneor anthracene moiety,

n is an integer of from 1 to 4; and

Ar, R₇, R₉, and R₉ are independently selected aryl groups.

In a typical embodiment at least one of Ar, R₇, R₈, and R₉ is apolycyclic fused ring structure, e.g., a naphthalene.

Another class of the hole-transporting material comprises a material offormula (E):

In formula (E), Ar₁-Ar₆ independently represent aromatic groups, forexample, phenyl groups or tolyl groups;

R₁-R₁₂ independently represent hydrogen or independently selectedsubstituent, for example an alkyl group containing from 1 to 4 carbonatoms, an aryl group, a substituted aryl group.

The various alkyl, alkylene, aryl, and arylene moieties of the foregoingstructural Formulae (A), (B), (C), (D), and (E) can each in turn besubstituted. Typical substituents include alkyl groups, alkoxy groups,aryl groups, aryloxy groups, and halogen such as fluoride, chloride, andbromide. The various alkyl and alkylene moieties typically contain fromabout 1 to 6 carbon atoms. The cycloalkyl moieties can contain from 3 toabout 10 carbon atoms, but typically contain five, six, or seven ringcarbon atoms, e.g. cyclopentyl, cyclohexyl, and cycloheptyl ringstructures. The aryl and arylene moieties are typically phenyl andphenylene moieties.

The HTL is formed of a single or a mixture of aromatic tertiary aminecompounds. Specifically, one can employ a triarylamine, such as atriarylamine satisfying the Formula (B), in combination with atetraaryldiamine, such as indicated by Formula (D). When a triarylamineis employed in combination with a tetraaryldiamine, the latter ispositioned as a layer interposed between the tiarylamine and theelectron injecting and transporting layer. Aromatic tertiary amines areuseful as hole-injecting materials also. Illustrative of useful aromatictertiary amines are the following:

-   1,1-bis(4-di-p-tolylaminophenyl)cyclohexane;-   1,1-bis(4-di-p-tolylaminophenyl)-4-phenylcyclohexane;-   1,5-bis[N-(1-naphthyl)-N-phenylamino]naphthalene;-   2,6-bis(di-p-tolylamino)naphthalene;-   2,6-bis[di-(1-naphthyl)amino]naphthalene;-   2,6-bis[N-(1-naphthyl)-N-(2-naphthyl)amino]naphthalene;-   2,6-bis[N,N-di(2-naphthyl)amine]fluorene;-   4-(di-p-tolylamino)-4′-[4(di-p-tolylamino)-styryl]stilbene;-   4,4′-bis(diphenylamino)quadriphenyl;-   4,4″-bis[N-(1-anthryl)-N-phenylamino]-p-terphenyl;-   4,4′-bis[N-(1-coronenyl)-N-phenylamino]biphenyl;-   4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB);-   4,4′-bis[N-(1-naphthyl)-N-(2-naphthyl)amino]biphenyl (TNB);-   4,4″-bis[N-(1-naphthyl)-N-phenylamino]p-terphenyl;-   4,4′-bis[N-(2-naphthacenyl)-N-phenylamino]biphenyl;-   4,4′-bis[N-(2-naphthyl)-N-phenylamino]biphenyl;-   4,4′-bis[N-(2-perylenyl)-N-phenylamino]biphenyl;-   4,4′-bis[N-(2-phenanthryl)-N-phenylamino]biphenyl;-   4,4′-bis[N-(2-pyrenyl)-N-phenylamino]biphenyl;-   4,4′-bis[N-(3-acenaphthenyl)-N-phenylamino]biphenyl;-   4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl (TPD);-   4,4′-bis[N-(8-fluoranthenyl)-N-phenylamino]biphenyl;-   4,4′-bis[N-(9-anthryl)-N-phenylamino]biphenyl;-   4,4′-bis{N-phenyl-N-[4-(1-naphthyl)-phenyl]amino}biphenyl;-   4,4′-bis[N-phenyl-N-(2-pyrenyl)amino]biphenyl;-   4,4′,4″-tris[(3-methylphenyl)phenylamino]triphenylamine (m-TDATA);-   Bis(4-dimethylamino-2-methylphenyl)-phenylmethane;-   N-phenylcarbazole;-   N,N′-bis[4-([1,1-biphenyl]-4-ylphenylamino)phenyl]-N,N′-di-1-naphthalenyl-[1,1′-biphenyl]-4,4′-diamine;-   N,N′-bis[4-(di-1-naphthalenylamino)phenyl]-N,N-di-1-naphthalenyl-[1,1′-biphenyl]-4,4′-diamine;-   N,N′-bis[4-[(3-methylphenyl)phenylamino]phenyl]-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine;-   N,N-bis[4-(diphenylamino)phenyl]-N′,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine;-   N,N′-di-1-naphthalenyl-N,N′-bis[4-(1-naphthalenylphenylamino)phenyl]-[1,1′-biphenyl]-4,4′-diamine;-   N,N′-di-1-naphthalenyl-N,N′-bis[4-(2-naphthalenylphenylamino)phenyl]-[1,1′-biphenyl]-4,4′-diamine;-   N,N,N-tri(p-tolyl)amine;-   N,N,N′,N′-tetra-p-tolyl-4-4′-diaminobiphenyl;-   N,N,N′,N′-tetraphenyl-4,4′-diaminobiphenyl;-   N,N,N′,N′-tetra-1-naphthyl-4,4′-diaminobiphenyl;-   N,N,N′,N′-tetra-2-naphthyl-4,4′-diaminobiphenyl; and-   N,N,N′,N′-tetra(2-naphthyl)-4,4″-diamino-p-terphenyl.

Another class of useful hole-transporting materials includes polycyclicaromatic compounds as described in EP 1 009 041. Tertiary aromaticamines with more than two amine groups can be used including oligomericmaterials. In addition, polymeric hole-transporting materials are usedsuch as poly(N-vinylcarbazole) (PVK), polythiophenes, polypyrrole,polyaniline, and copolymers such aspoly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) also calledPEDOT/PSS.

The thickness of the HTL 132 is in the range of from 5 nm to 200 nm,preferably, in the range of from 10 nm to 150 nm.

Exciton Blocking Layer (EBL)

An optional exciton- or electron-blocking layer may be present betweenthe HTL and the LEL (not shown in FIG. 1). Some suitable examples ofsuch blocking layers are described in U.S. App 20060134460 A1.

Light Emitting Layer

As more fully described in U.S. Pat. Nos. 4,769,292 and 5,935,721, thelight-emitting layer(s) (LEL) 134 of the organic EL element shown inFIG. 1 comprises a luminescent, fluorescent or phosphorescent materialwhere electroluminescence is produced as a result of electron-hole pairrecombination in this region. The light-emitting layer can be comprisedof a single material, but more commonly consists ofnon-electroluminescent compounds (generally referred to as the host)doped with an electroluminescent or light-emitting guest compound(generally referred to as the dopant) or compounds where light emissioncomes primarily from the electroluminescent compound and can be of anycolor. In this invention, the light-emitting material is a fluoranthenederivative. The electroluminescent fluoranthene compounds can be coatedas 0.01 to less than 50% by volume into the non-electroluminescentcomponent material, but typically coated as 0.01 to 30% and moretypically coated as 0.01 to 15% into the non-electroluminescentcomponent. In this invention, the most desirable range for thefluoranthene compound is 1 to 12%. The thickness of the LEL can be anysuitable thickness. It can be in the range of from 0.1 mm to 100 mm.

A LEL can be a single light-emitting layer or a light-emitting zonecomposed of a series of individual light-emitting sublayers. Thesesublayers can emit the same or different colors of light.

An important relationship for choosing a dye as a electroluminescentcomponent is a comparison of the bandgap potential which is defined asthe energy difference between the highest occupied molecular orbital andthe lowest unoccupied molecular orbital of the molecule. For efficientenergy transfer from the non-electroluminescent compound to theelectroluminescent compound molecule, a necessary condition is that theband gap of the electroluminescent compound is smaller than that of thenon-electroluminescent compound or compounds. Thus, the selection of anappropriate host material is based on its electronic characteristicsrelative to the electronic characteristics of the electroluminescentcompound, which itself is chosen for the nature and efficiency of thelight emitted. As described below, fluorescent and phosphorescentdopants typically have different electronic characteristics so that themost appropriate hosts for each may be different. However in some cases,the same host material can be useful for either type of dopant.

Non-electroluminescent compounds and emitting molecules known to be ofuse include, but are not limited to, those disclosed in U.S. Pat. No.4,768,292, U.S. Pat. No. 5,141,671, U.S. Pat. No. 5,150,006, U.S. Pat.No. 5,151,629, U.S. Pat. No. 5,405,709, U.S. Pat. No. 5,484,922, U.S.Pat. No. 5,593,788, U.S. Pat. No. 5,645,948, U.S. Pat. No. 5,683,823,U.S. Pat. No. 5,755,999, U.S. Pat. No. 5,928,802, U.S. Pat. No.5,935,720, U.S. Pat. No. 5,935,721, and U.S. Pat. No. 6,020,078.

a) Phosphorescent Light Emitting Layers

Suitable hosts for phosphorescent LELs should be selected so thattransfer of a triplet exciton can occur efficiently from the host to thephosphorescent dopant(s) but cannot occur efficiently from thephosphorescent dopant(s) to the host. Therefore, it is highly desirablethat the triplet energy of the host be higher than the triplet energiesof phosphorescent dopant. Generally speaking, a large triplet energyimplies a large optical band gap. However, the band gap of the hostshould not be chosen so large as to cause an unacceptable barrier toinjection of holes into the fluorescent blue LEL and an unacceptableincrease in the drive voltage of the OLED. The host in a phosphorescentLEL may include any of the aforementioned hole-transporting materialused for the HTL 132, as long as it has a triplet energy higher thanthat of the phosphorescent dopant in the layer. The host used in aphosphorescent LEL can be the same as or different from thehole-transporting material used in the HTL 132. In some cases, the hostin the phosphorescent LEL may also suitably include anelectron-transporting material (it will be discussed thereafter), aslong as it has a triplet energy higher than that of the phosphorescentdopant.

In addition to the aforementioned hole-transporting materials in the HTL132, there are several other classes of hole-transporting materialssuitable for use as the host in a phosphorescent LEL.

One desirable host comprises a hole-transporting material of formula(F):

In formula (F), R₁ and R₂ represent substituents, provided that R₁ andR₂ can join to form a ring. For example, R₁ and R₂ can be methyl groupsor join to form a cyclohexyl ring;

Ar₁-Ar₄ represent independently selected aromatic groups, for examplephenyl groups or tolyl groups;

R₃-R₁₀ independently represent hydrogen, alkyl, substituted alkyl, aryl,substituted aryl group.

Examples of suitable materials include, but are not limited to:

-   1,1-Bis(4-(N,N-di-p-tolylamino)phenyl)cyclohexane (TAPC);-   1,1-Bis(4-(N,N-di-p-tolylaminophenyl)cyclopentane;-   4,4′-(9H-fluoren-9-ylidene)bis[N,N-bis(4-methylphenyl)-benzenamine;-   1,1-Bis(4-(N,N-di-p-tolylamino)phenyl)-4-phenylcyclohexane;-   1,1-Bis(4-(N,N-di-p-tolylamino)phenyl)-4-methylcyclohexane;-   1,1-Bis(4-(N,N-di-p-tolylamino)phenyl)-3-phenylpropane;-   Bis[4-(N,N-diethylamino)-2-methylphenyl](4-methylpenyl)methane;-   Bis[4-(N,N-diethylamino)-2-methylphenyl](4-methylphenyl)ethane;-   4-(4-Diethylaminophenyl)triphenylmethane;-   4,4′-Bis(4-diethylaminophenyl)diphenylmethane.

A useful class of triarylamines suitable for use as the host includescarbazole derivatives such as those represented by formula (G):

In formula (G), Q independently represents nitrogen, carbon, an arylgroup, or substituted aryl group, preferably a phenyl group;

R₁ is preferably an aryl or substituted aryl group, and more preferablya phenyl group, substituted phenyl, biphenyl, substituted biphenylgroup;

R₂ through R₇ are independently hydrogen, alkyl, phenyl or substitutedphenyl group, aryl amine, carbazole, or substituted carbazole;

and n is selected from 1 to 4.

Another useful class of carbazoles satisfying structural formula (G) isrepresented by formula (H):

wherein:

n is an integer from 1 to 4;

Q is nitrogen, carbon, an aryl, or substituted aryl;

R₂ through R₇ are independently hydrogen, an allyl group, phenyl orsubstituted phenyl, an aryl amine, a carbazole and substitutedcarbazole.

Illustrative of useful substituted carbazoles are the following:

-   4-(9H-carbazol-9-yl)-N,N-bis[4-(9H-carbazol-9-yl)phenyl]-benzenamine    (TCTA);-   4-(3-phenyl-9H-carbazol-9-yl)-N,N-bis[4(3-phenyl-9H-carbazol-9-yl)phenyl]-benzenamine;-   9,9′-[5′-[4-(9H-carbazol-9-yl)phenyl][1,1′:3′,1″-terphenyl]-4,4″-diyl]bis-9H-carbazole.-   9,9′-(2,2′-dimethyl[1,1′-biphenyl]-4,4′-diyl)bis-9H-carbazole    (CDBP);-   9,9′-[1,1′-biphenyl]-4,4′-diylbis-9H-carbazole (CBP);-   9,9′-(1,3-phenylene)bis-9H-carbazole (mCP);-   9,9′-(1,4-phenylene)bis-9H-carbazole;-   9,9′,9″-(1,3,5-benzenetriyl)tris-9H-carbazole;-   9,9′-(1,4-phenylene)bis[N,N′,N′-tetraphenyl-9H-carbazole-3,6-diamine;-   9-[4-(9H-carbazol-9-yl)phenyl]-N,N-diphenyl-9H-carbazol-3-amine;-   9,9′-(1,4-phenylene)bis[N,N-diphenyl-9H-carbazol-3-amine;-   9-[4-(9H-carbazol-9-yl)phenyl]-N,N,N′,N′-tetraphenyl-9H-carbazole-3,6-diamine.

The above classes of hosts suitable for phosphorescent LELs may also beused as hosts in fluorescent LELs as well.

Suitable phosphorescent dopants for use in a phosphorescent LEL can beselected from the phosphorescent materials described by formula (J)below:

wherein:

A is a substituted or unsubstituted heterocyclic ring containing atleast one nitrogen atom;

B is a substituted or unsubstituted aromatic or heteroaromatic ring, orring containing a vinyl carbon bonded to M;

X-Y is an anionic bidentate ligand;

m is an integer from 1 to 3 and

n in an integer from 0 to 2 such that m+n=3 for M=Rh or Ir; or

m is an integer from 1 to 2 and n in an integer from 0 to 1 such thatm+n=2 for M=Pt or Pd.

Compounds according to formula (J) may be referred to as C,N— (or C^N—)cyclometallated complexes to indicate that the central metal atom iscontained in a cyclic unit formed by bonding the metal atom to carbonand nitrogen atoms of one or more ligands. Examples of heterocyclic ringA in formula (J) include substituted or unsubstituted pyridine,quinoline, isoquinoline, pyrimidine, indole, indazole, thiazole, andoxazole rings. Examples of ring B in formula (J) include substituted orunsubstituted phenyl, napthyl, thienyl, benzothienyl, furanyl rings.Ring B in formula (J) may also be a N-containing ring such as pyridine,with the proviso that the N-containing ring bonds to M through a C atomas shown in formula (J) and not the N atom.

An example of a tris-C,N-cyclometallated complex according to formula(J) with m=3 and n=0 is tris(2-phenyl-pyridinato-N,C^(2′))iridium (III),shown below in stereodiagrams as facial (fac-) or meridional (mer-)isomers.

Generally, facial isomers are preferred since they are often found tohave higher phosphorescent quantum yields than the meridional isomers.Additional examples of tris-C,N-cyclometallated phosphorescent materialsaccording to formula (J) aretris(2-(4′-methylphenyl)pyridinato-N,C^(2′))Iridium(III),tris(3-phenylisoquinolinato-N,C^(2′))Iridium(III),tris(2-phenylquinolinato-N,C^(2′))Iridium(II),tris(1-phenylisoquinolinato-N,C^(2′))Iridium(III),tris(1-(4′-methylphenyl)isoquinolinato-N,C^(2′))Iridium(III),tris(2-(4′,6′-difluorophenyl)-pyridinato-N,C^(2′))Iridium(III),tris(2-((5′-phenyl)-phenyl)pyridinato-N,C^(2′))Iridium(III),tris(2-(2′-benzothienyl)pyridinato-N,C^(3′))Iridium(III),tris(2-phenyl-3,3′dimethyl)indolato-N,C^(2′))Ir(III),tris(1-phenyl-1H-indazolato-N,C^(2′))Ir(III).

Of these, tris(1-phenylisoquinoline) iridium (III) (also referred to asIr(piq)₃) and tris(2-phenylpyridine) iridium (also referred to asIr(ppy)₃) are particularly suitable for this invention.

Tris-C,N-cyclometallated phosphorescent materials also include compoundsaccording to formula (J) wherein the monoanionic bidentate ligand X-Y isanother C,N-cyclometallating ligand. Examples includebis(1-phenylisoquinolinato-N,C^(2′))(2-phenylpyridinato-N,C²)Iridium(III)and bis(2-phenylpyridinato-N,C^(2′))(1-phenylisoquinolinato-N,C²)Iridium(III). Synthesis of suchtris-C,N-cyclometallated complexes containing two differentC,N-cyclometallating ligands may be conveniently synthesized by thefollowing steps. First, a bis-C,N-cyclometallated diiridium dihalidecomplex (or analogous dirhodium complex) is made according to the methodof Nonoyama (Bull. Chem. Soc. Jpn., 47, 767 (1974)). Secondly, a zinccomplex of the second, dissimilar C,N-cyclometallating ligand isprepared by reaction of a zinc halide with a lithium complex or Grignardreagent of the cyclometallating ligand. Third, the thus formed zinccomplex of the second C,N-cyclometallating ligand is reacted with thepreviously obtained bis-C,N-cyclometallated diiridium dihalide complexto form a tris-C,N-cyclometallated complex containing the two differentC,N-cyclometallating ligands. Desirably, the thus obtainedtris-C,N-cyclometallated complex containing the two differentC,N-cyclometallating ligands may be converted to an isomer wherein the Catoms bonded to the metal (e.g. Ir) are all mutually cis by heating in asuitable solvent such as dimethyl sulfoxide.

Suitable phosphorescent materials according to formula (J) may inaddition to the C,N-cyclometallating ligand(s) also contain monoanionicbidentate ligand(s) X-Y that are not C,N-cyclometallating. Commonexamples are beta-diketonates such as acetylacetonate, and Schiff basessuch as picolinate. Examples of such mixed ligand complexes according toformula (J) includebis(2-phenylpyridinato-N,C²)Iridium(III)(acetylacetonate),bis(2-(2′-benzothienyl)pyridinato-N,C^(3′))Iridium(III)(acetylacetonate),andbis(2-(4′,6′-difluorophenyl)-pyridinato-N,C²)Iridium(III)(picolinate).

Other important phosphorescent materials according to formula (J)include C,N-cyclometallated Pt(II) complexes such ascis-bis(2-phenylpyridinato-N,C^(2′))platinum(II),cis-bis(2-(2′-thienyl)pyridinato-N,C^(3′)) platinum(II),cis-bis(2-(2′-thienyl)quinolinato-N,C^(5′)) platinum(II), or(2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)) platinum (II)(acetylacetonate).

The emission wavelengths (color) of C,N-cyclometallated phosphorescentmaterials according to formula (J) are governed principally by thelowest energy optical transition of the complex and hence by the choiceof the C,N-cyclometallating ligand. For example,2-phenyl-pyridinato-N,C^(2′) complexes are typically green emissivewhile 1-phenyl-isoquinolinolato-N,C^(2′) complexes are typically redemissive. In the case of complexes having more than oneC,N-cyclometallating ligand, the emission will be that of the ligandhaving the property of longest wavelength emission. Emission wavelengthsmay be further shifted by the effects of substituent groups on theC,N-cyclometallating ligands. For example, substitution of electrondonating groups at appropriate positions on the N-containing ring A orelectron accepting groups on the C-containing ring B tend to blue-shiftthe emission relative to the unsubstituted C,N-cyclometallated ligandcomplex. Selecting a monodentate anionic ligand X,Y in formula (J)having more electron accepting properties also tends to blue-shift theemission of a C,N-cyclometallated ligand complex. Examples of complexeshaving both monoanionic bidentate ligands possessing electron acceptingproperties and electron accepting substituent groups on the C-containingring B includebis(2-(4′,6′-difluorophenyl)-pyridinato-N,C²)iridium(III)(picolinate)andbis(2-(4′,6′-difluorophenyl)-pyridinato-N,C^(2′))iridium(III)(tetrakis(1-pyrazolyl)borate).

The central metal atom in phosphorescent materials according to formula(J) may be Rh or Ir (m+n=3) and Pd or Pt (m+n=2). Preferred metal atomsare Ir and Pt since they tend to give higher phosphorescent quantumefficiencies according to the stronger spin-orbit coupling interactionsgenerally obtained with elements in the third transition series.

In addition to bidentate C,N-cyclometallating complexes represented byformula (J), many suitable phosphorescent materials contain multidentateC,N-cyclometallating ligands. Phosphorescent materials having tridentateligands suitable for use in the present invention are disclosed in U.S.Pat. No. 6,824,895 B1 and references therein, incorporated in theirentirety herein by reference. Phosphorescent materials havingtetradentate ligands suitable for use in the present invention aredescribed by the following formulae:

wherein:

M is Pt or Pd;

R¹-R⁷ represent hydrogen or independently selected substituents,provided that R¹ and R², R² and R³, R³ and R⁴, R⁴ and R⁵, R⁵ and R⁶, aswell as R⁶ and R⁷ may join to form a ring group;

R⁸-R¹⁴ represent hydrogen or independently selected substituents,provided that R⁸ and R⁹, R¹¹ and R¹⁰, R¹⁰ and R¹¹, R¹¹ and R¹², R¹² andR¹³, as well as R¹³ and R¹⁴, may join to form a ring group;

E represents a bridging group selected from the following:

wherein:

R and R′ represent hydrogen or independently selected substituents;provided R and R′ may combine to form a ring group.

One desirable tetradentate C,N-cyclometallated phosphorescent materialsuitable for use in as the phosphorescent dopant is represented by thefollowing formula:

wherein:

R¹-R⁷ represent hydrogen or independently selected substituents,provided that R¹ and R², R² and R³, R³ and R⁴, R⁴ and R⁵, R⁵ and R⁶, aswell as R⁶ and R⁷ may combine to form a ring group;

R⁸-R¹⁴ represent hydrogen or independently selected substituents,provided that R⁸ and R⁹, R⁹ and R¹⁰, R¹⁰ and R¹¹, R¹¹ and R¹², R¹² andR¹³, as well as R¹³ and R¹⁴ may combine to form a ring group;

Z¹-Z⁵ represent hydrogen or independently selected substituents,provided that Z¹ and Z², Z² and Z³, Z³ and Z⁴, as well as Z⁴ and Z⁵ maycombine to form a ring group.

Specific examples of phosphorescent materials having tetradentateC,N-cyclometallating ligands suitable for use in the present inventioninclude compounds (M-1), (M-2) and (M-3) represented below.

Phosphorescent materials having tetradentate C,N-cyclometallatingligands may be synthesized by reacting the tetradentateC,N-cyclometallating ligand with a salt of the desired metal, such asK₂PtCl₄, in a proper organic solvent such as glacial acetic acid to formthe phosphorescent material having tetradentate C,N-cyclometallatingligands. A tetraalkylammonium salt such as tetrabutylammonium chloridecan be used as a phase transfer catalyst to accelerate the reaction.

Other phosphorescent materials that do not involve C,N-cyclometallatingligands are known. Phosphorescent complexes of Pt(II), Ir(I), and Rh(I)with maleonitriledithiolate have been reported (Johnson et al., J. Am.Chem. Soc., 105, 1795 (1983)). Re(I) tricarbonyl diimine complexes arealso known to be highly phosphorescent (Wrighton and Morse, J. Am. Chem.Soc., 96, 998 (1974); Stufkens, Comments Inorg. Chem., 13, 359 (1992);Yam, Chem. Commun., 789 (2001)). Os(II) complexes containing acombination of ligands including cyano ligands and bipyridyl orphenanthroline ligands have also been demonstrated in a polymer OLED (Maet al., Synthetic Metals, 94, 245 (1998)).

Porphyrin complexes such as2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine platinum(II) are alsouseful phosphorescent dopant.

Still other examples of useful phosphorescent materials includecoordination complexes of the trivalent lanthanides such as Th³⁺ andEu³⁺ (Kido et al., Chem. Lett., 657 (1990); J. Alloys and Compounds,192, 30 (1993); Jpn. J. Appl. Phys., 35, L394 (1996) and Appl. Phys.Lett., 65, 2124 (1994)).

The phosphorescent dopant in a phosphorescent LEL is typically presentin an amount of from 1 to 20% by volume of the LEL, and convenientlyfrom 2 to 8% by volume of the LEL. In some embodiments, thephosphorescent dopant(s) may be attached to one or more host materials.The host materials may further be polymers. The phosphorescent dopant inthe first phosphorescent light-emitting layer is selected from green andred phosphorescent materials.

The thickness of a phosphorescent LEL is greater than 0.5 nm,preferably, in the range of from 1.0 nm to 40 nm.

b) Fluorescent Light Emitting Layers

Although the term “fluorescent” is commonly used to describe anylight-emitting material, in this case it refers to a material that emitslight from a singlet excited state. Fluorescent materials may be used inthe same layer as the phosphorescent material, in adjacent layers, inadjacent pixels, or any combination. Care must be taken not to selectmaterials that will adversely affect the performance of thephosphorescent materials of this invention. One skilled in the art willunderstand that concentrations and triplet energies of materials in thesame layer as the phosphorescent material or in an adjacent layer mustbe appropriately set so as to prevent unwanted quenching of thephosphorescence.

Typically, a fluorescent LEL includes at least one host and at least onefluorescent dopant. The host may be a hole-transporting material or anyof the suitable hosts for phosphorescent dopants as defined above or maybe an electron-transporting material as defined below.

The dopant is typically chosen from highly fluorescent dyes, e.g.,transition metal complexes as described in WO 98/55561 A1, WO 00/18851A1, WO 00/57676 A1, and WO 00/70655.

Useful fluorescent dopants include, but are not limited to, derivativesof anthracene, tetracene, xanthene, perylene, phenylene,dicyanomethylenepyran compounds, thiopyran compounds, polymethinecompounds, pyrylium and thiapyrylium compounds, arylpyrene compounds,arylenevinylene compounds, periflanthene derivatives, indenoperylenederivatives, bis(azinyl)amine boron compounds, bis(azinyl)methane boroncompounds, distryrylbenzene derivatives, distyrylbiphenyl derivatives,distyrylamine derivatives and carbostyryl compounds.

Some fluorescent emitting materials include, but are not limited to,derivatives of anthracene, tetracene, xanthene, perylene, rubrene,coumarin, rhodamine, and quinacridone, dicyanomethylenepyran compounds,thiopyran compounds, polymethine compounds, pyrylium and thiapyryliumcompounds, fluorene derivatives, periflanthene derivatives,indenoperylene derivatives, bis(azinyl)amine boron compounds,bis(azinyl)methane compounds (as described in U.S. Pat. No. 5,121,029)and carbostyryl compounds. Illustrative examples of useful materialsinclude, but are not limited to, the following:

X R1 R2 FD-9 O H H FD-10 O H Methyl FD-11 O Methyl H FD-12 O MethylMethyl FD-13 O H t-butyl FD-14 O t-butyl H FD-15 O t-butyl t-butyl FD-16S H H FD-17 S H Methyl FD-18 S Methyl H FD-19 S Methyl Methyl FD-20 S Ht-butyl FD-21 S t-butyl H FD-22 S t-butyl t-butyl

X R1 R2 FD-13 O H H FD-24 O H Methyl FD-25 O Methyl H FD-26 O MethylMethyl FD-27 O H t-butyl FD-28 O t-butyl H FD-29 O t-butyl t-butyl FD-30S H H FD-31 S H Methyl FD-32 S Methyl H FD-33 S Methyl Methyl FD-34 S Ht-butyl FD-35 S t-butyl H FD-36 S t-butyl t-butyl

R FD-37 phenyl FD-38 methyl FD-39 t-butyl FD-40 mesityl

R FD-41 phenyl FD-42 methyl FD-43 t-butyl FD-44 mesityl

Preferred fluorescent blue dopants may be found in Chen, Shi, and Tang,“Recent Developments in Molecular Organic Electroluminescent Materials,”Macromol. Symp. 125, 1 (1997) and the references cited therein; Hung andChen, “Recent Progress of Molecular Organic Electroluminescent Materialsand Devices,” Mat. Sci. and Eng. R39, 143 (2002) and the referencescited therein. It should be noted that FD-46 and FD-49 are fluoranthenederivatives with annulated rings.

A particularly preferred class of blue-emitting fluorescent dopants isrepresented by Formula (N), known as a bis(azinyl)amine borane complex,and is described in U.S. Pat. No. 6,661,023.

wherein:

A and A′ represent independent azine ring systems corresponding to6-membered aromatic ring systems containing at least one nitrogen;

each X^(a) and X^(b) is an independently selected substituent, two ofwhich may join to form a fused ring to A or A′;

m and n are independently 0 to 4;

Z^(a) and Z^(b) are independently selected substituents; and

1, 2, 3, 4, 1′, 2′, 3′, and 4′ are independently selected as eithercarbon or nitrogen atoms.

Desirably, the azine rings are either quinolinyl or isoquinolinyl ringssuch that 1, 2, 3, 4, 1′, 2′, 3′, and 4′ are all carbon; m and n areequal to or greater than 2; and X^(a) and X^(b) represent at least twocarbon substituents which join to form an aromatic ring. Desirably,Z^(a) and Z^(b) are fluorine atoms.

Preferred embodiments further include devices where the two fused ringsystems are quinoline or isoquinoline systems; the aryl or heterocyclicsubstituent is a phenyl group; there are present at least two X^(a)groups and two X^(b) groups which join to form a 6-6 fused ring, thefused ring systems are fused at the 1-2, 3-4, 1′-2′, or 3′-4′ positions,respectively; one or both of the fused rings is substituted by a phenylgroup; and where the dopant is depicted in Formulae (N-a), (N-b), or(N-c).

wherein:

each X^(c), X^(d), X^(e), X^(f), X^(g), and X^(h) is hydrogen or anindependently selected substituent, one of which must be an aryl orheterocyclic group.

Desirably, the azine rings are either quinolinyl or isoquinolinyl ringssuch that 1, 2, 3, 4, 1′, 2′, 3′, and 4′ are all carbon; m and n areequal to or greater than 2; and X^(a) and X^(b) represent at least twocarbon substituents which join to form an aromatic ring, and one is anaryl or substituted aryl group. Desirably, Z^(a) and Z^(b) are fluorineatoms.

Of these, compound FD-54 is particularly useful.

Coumarins represent a useful class of green-emitting dopants asdescribed by Tang et al. in U.S. Pat. Nos. 4,769,292 and 6,020,078.Green dopants or light-emitting materials can be coated as 0.01 to 50%by weight into the host material, but typically coated as 0.01 to 30%and more typically coated as 0.01 to 15% by weight into the hostmaterial. Examples of useful green-emitting coumarins include C545T andC545TB. Quinacridones represent another useful class of green-emittingdopants. Useful quinacridones are described in U.S. Pat. No. 5,593,788,publication JP 09-13026A, and commonly assigned U.S. patent applicationSer. No. 10/184,356 filed Jun. 27, 2002 by Lelia Cosimbescu, entitled“Device Containing Green Organic Light-Emitting Diode”, the disclosureof which is incorporated herein.

Examples of particularly useful green-emitting quinacridones are FD-7and FD-8.

Formula (N-d) below represents another class of green-emitting dopantsuseful in the invention.

wherein:

A and A′ represent independent azine ring systems corresponding to6-membered aromatic ring systems containing at least one nitrogen;

each X^(a) and X^(b) is an independently selected substituent, two ofwhich may join to form a fused ring to A or A′;

m and n are independently 0 to 4;

Y is H or a substituent;

Z^(a) and Z^(b) are independently selected substituents; and

1, 2, 3, 4, 1′, 2′, 3′, and 4′ are independently selected as eithercarbon or nitrogen atoms.

In the device, 1, 2, 3, 4, 1′, 2′, 3′, and 4′ are conveniently allcarbon atoms. The device may desirably contain at least one or both ofring A or A′ that contains substituents joined to form a fused ring. Inone useful embodiment, there is present at least one X^(a) or X^(b)group selected from the group consisting of halide and alkyl, aryl,alkoxy, and aryloxy groups. In another embodiment, there is present aZ^(a) and Z^(b) group independently selected from the group consistingof fluorine and alkyl, aryl, alkoxy and aryloxy groups. A desirableembodiment is where Z^(a) and Z^(b) are F. Y is suitably hydrogen or asubstituent such as an alkyl, aryl, or heterocyclic group.

The emission wavelength of these compounds may be adjusted to someextent by appropriate substitution around the central bis(azinyl)metheneboron group to meet a color aim, namely green. Some examples of usefulmaterial are FD-50, FD-51 and FD-52.

Naphthacenes and derivatives thereof also represent a useful class ofemitting dopants, which can also be used as stabilizers. These dopantmaterials can be coated as 0.01 to 50% by weight into the host material,but typically coated as 0.01 to 30% and more typically coated as 0.01 to15% by weight into the host material. Naphthacene derivative YD-1(t-BuDPN) below, is an example of a dopant material used as astabilizer.

Some examples of this class of materials are also suitable as hostmaterials as well as dopants. For example, see U.S. Pat. No. 6,773,832or U.S. Pat. No. 6,720,092. A specific example of this would be rubrene(FD-5).

Another class of useful dopants are perylene derivatives; for examplesee U.S. Pat. No. 6,689,493. A specific examples is FD-46.

Metal complexes of 8-hydroxyquinoline and similar derivatives (FormulaO) constitute one class of useful non-electroluminescent host compoundscapable of supporting electroluminescence, and are particularly suitablefor light emission of wavelengths longer than 500 nm, e.g., green,yellow, orange, and red.

wherein:

M represents a metal;

n is an integer of from 1 to 4; and

Z independently in each occurrence represents the atoms completing anucleus having at least two fused aromatic rings.

From the foregoing it is apparent that the metal can be monovalent,divalent, trivalent, or tetravalent metal. The metal can, for example,be an alkali metal, such as lithium, sodium, or potassium; an alkalineearth metal, such as magnesium or calcium; an earth metal, such asaluminum or gallium, or a transition metal such as zinc or zirconium.Generally any monovalent, divalent, trivalent, or tetravalent metalknown to be a useful chelating metal can be employed.

Z completes a heterocyclic nucleus containing at least two fusedaromatic rings, at least one of which is an azole or azine ring.Additional rings, including both aliphatic and aromatic rings, can befused with the two required rings, if required. To avoid addingmolecular bulk without improving on function the number of ring atoms isusually maintained at 18 or less.

Illustrative of useful chelated oxinoid compounds are the following:

-   O-1: Aluminum trisoxine [alias, tris(8-quinolinolato)aluminum(III)]-   O-2: Magnesium bisoxine [alias, bis(8-quinolinolato)magnesium(II)]-   O-3: Bis[benzo{f}-8-quinolinolato]zinc (II)-   O-4:    Bis(2-methyl-8-quinolinolato)aluminum(III)-μ-oxo-bis(2-methyl-8-quinolinolato)    aluminum(III)-   O-5: Indium trisoxine [alias, tris(8-quinolinolato)indium]-   O-6: Aluminum tris(5-methyloxine) [alias,    tris(5-methyl-8-quinolinolato) aluminum(III)]-   O-7: Lithium oxine [alias, (8-quinolinolato)lithium(I)]-   O-8: Gallium oxine [alias, tris(8-quinolinolato)gallium(III)]-   O-9: Zirconium oxine [alias, tetra(8-quinolinolato)zirconium(IV)]-   O-10: Bis(2-methyl-8-quinolinato)-4-phenylphenolatoaluminum (III)

Anthracene derivatives according to formula (P) are also very usefulhost materials in the LEL:

wherein:

R₁-R₁₀ are independently chosen from hydrogen, alkyl groups from 1-24carbon atoms or aromatic groups from 1-24 carbon atoms. Particularlypreferred are compounds where R₁ and R₆ are phenyl, biphenyl or napthyl,R₃ is phenyl, substituted phenyl or napthyl and R₂, R₄, R₅, R₇-R₁₀ areall hydrogen. Such anthracene hosts are known to have excellent electrontransporting properties.

Particularly desirable are derivatives of9,10-di-(2-naphthyl)anthracene. Illustrative examples include9,10-di-(2-naphthyl)anthracene (ADN) and2-t-butyl-9,10-di-(2-naphthyl)anthracene (TBADN). Other anthracenederivatives can be useful as a non-electroluminescent compound in theLEL, such as diphenylanthracene and its derivatives, as described inU.S. Pat. No. 5,927,247. Styrylarylene derivatives as described in U.S.Pat. No. 5,121,029 and JP 08333569 are also usefulnon-electroluminescent materials. For example,9,10-bis[4-(2,2-diphenylethenyl)phenyl]anthracene,4,4′-Bis(2,2-diphenylethenyl)-1,1′-biphenyl (DPVBi) and phenylanthracenederivatives as described in EP 681,019 are useful non-electroluminescentmaterials.

Some illustrative examples of suitable anthracenes are:

Spacer Layer

Spacer layers, when present, are located in direct contact to a LEL.They may be located on either the anode or cathode side, or even bothsides of the LEL. They typically do not contain any light-emissivedopants. One or more materials may be used and could be either ahole-transporting material as defined above or an electron-transportingmaterial as defined below. If located next to a phosphorescent LEL, thematerial in the spacer layer should have higher triplet energy than thatof the phosphorescent dopant in the LEL. Most desirably, the material inthe spacer layer will be the same as used as the host in the adjacentLEL. Thus, any of the host materials described as also suitable for usein a spacer layer. The spacer layer should be thin; at least 0.1 nm, butpreferably in the range of from 1.0 nm to 20 nm.

Hole-Blocking Layer (HBL)

When a LEL containing a phosphorescent emitter is present, it isdesirable to locate a hole-blocking layer 135 between theelectron-transporting layer 136 and the light-emitting layer 134 to helpconfine the excitons and recombination events to the LEL. In this case,there should be an energy barrier for hole migration from co-hosts intothe hole-blocking layer, while electrons should pass readily from thehole-blocking layer into the light-emitting layer comprising co-hostmaterials and a phosphorescent emitter. It is further desirable that thetriplet energy of the hole-blocking material be greater than that of thephosphorescent material. Suitable hole-blocking materials are describedin WO 00/70655A2, WO 01/41512 and WO 01/93642 A1. Two examples of usefulhole blocking materials are bathocuproine (BCP) andbis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (BAlq).Metal complexes other than BAlq are also known to block holes andexcitons as described in US 20030068528. When a hole-blocking layer isused, its thickness can be between 2 and 100 nm and suitably between 5and 10 nm.

Electron Transporting Layer

The purpose of an electron-transporting layer is to allow efficientmovement of electrons from the cathode to the LEL. As such, it does notemit substantial amounts of light.

In one embodiment, the electron-transporting layer 136 may be composedonly of the fluoranthene derivative or may be a mixture of thefluoranthene with other appropriate materials. The % volume ratio offluoranthene to additional material can be anywhere from 1% to 99%, moresuitably at least 10% and typically, at least 30%. The fluoranthene orany additional materials used may be the same or different than used asin the LEL. If an organic lithium EIM is present, it may be the same ordifferent as used in the EIL.

The anthracene class of electron-transporting materials can also be usedin the ETL with or without the fluoranthene of the invention. Theseanthracene electron transporting derivatives are represented by Formula(P) as described above in connection with host materials for a LEL. Theanthracene in the ETL can be the same or different from that used in theLEL.

In addition to any of the electron-transporting materials previouslydescribed, any other materials known to be suitable for use in the ETLmay be used. Included are, but are not limited to, chelated oxinoidcompounds, anthracene derivatives, pyridine-based materials, imidazoles,oxazoles, thiazoles and their derivatives, polybenzobisazoles,cyano-containing polymers and perfluorinated materials. Otherelectron-transporting materials include various butadiene derivatives asdisclosed in U.S. Pat. No. 4,356,429 and various heterocyclic opticalbrighteners as described in U.S. Pat. No. 4,539,507.

A preferred class of benzazoles is described by Shi et al. in U.S. Pat.Nos. 5,645,948 and 5,766,779. Such compounds are represented bystructural formula (Q):

In formula (Q), n is selected from 2 to 8 and i is selected from 1-5;

Z is independently O, NR or S;

R is individually hydrogen; alkyl of from 1 to 24 carbon atoms, forexample, propyl, t-butyl, heptyl, and the like; aryl or hetero-atomsubstituted aryl of from 5 to 20 carbon atoms, for example, phenyl andnaphthyl, furyl, thienyl, pyridyl, quinolinyl and other heterocyclicsystems; or halo such as chloro, fluoro; or atoms necessary to completea fused aromatic ring; and

X is a linkage unit consisting of carbon, alkyl, aryl, substitutedalkyl, or substituted aryl, which conjugately or unconjugately connectsthe multiple benzazoles together.

An example of a useful benzazole is2,2′,2″-(1,3,5-phenylene)tris[1-phenyl-1H-benzimidazole] (TPBI)represented by a formula (Q-1) shown below:

Another suitable class of the electron-transporting materials includesvarious substituted phenanthrolines as represented by formula (R):

In formula (R), R₁-R₈ are independently hydrogen, alkyl group, aryl orsubstituted aryl group, and at least one of R₁-R₈ is aryl group orsubstituted aryl group.

Examples of suitable materials are2,9-dimethyl-4,7-diphenyl-phenanthroline (BCP) (see formula (R-1)) and4,7-diphenyl-1,10-phenanthroline (Bphen) (see formula (R-2)).

Suitable triarylboranes that function as an electron-transportingmaterial may be selected from compounds having the chemical formula (S):

wherein:

Ar₁ to Ar₃ are independently an aromatic hydrocarbocyclic group or anaromatic heterocyclic group which may have a substituent. It ispreferable that compounds having the above structure are selected fromformula (S-1):

wherein:

R₁-R₁₅ are independently hydrogen, fluoro, cyano, trifluoromethyl,sulfonyl, alkyl, aryl or substituted aryl group.

Specific representative embodiments of the triarylboranes include:

The electron-transporting material may also be selected from substituted1,3,4-oxadiazoles of formula (T):

wherein:

R₁ and R₂ are individually hydrogen; alkyl of from 1 to 24 carbon atoms,for example, propyl, t-butyl, heptyl, and the like; aryl or hetero-atomsubstituted aryl of from 5 to 20 carbon atoms, for example, phenyl andnaphthyl, furyl, thienyl, pyridyl, quinolinyl and other heterocyclicsystems; or halo such as chloro, fluoro; or atoms necessary to completea fused aromatic ring.

Illustrative of the useful substituted oxadiazoles are the following:

The electron-transporting material may also be selected from substituted1,2,4-triazoles according to formula (U):

wherein:

R₁, R₂ and R₃ are independently hydrogen, alkyl group, aryl orsubstituted aryl group, and at least one of R₁-R₃ is aryl group orsubstituted aryl group. An example of a useful triazole is3-phenyl-4-(1-naphtyl)-5-phenyl-1,2,4-triazole represented by formula(U-1):

The electron-transporting material may also be selected from substituted1,3,5-triazines. Examples of suitable materials are:

-   2,4,6-tris(diphenylamino)-1,3,5-triazine;-   2,4,6-tricarbazolo-1,3,5-triazine;-   2,4,6-tris(N-phenyl-2-naphthylamino)-1,3,5-triazine;-   2,4,6-tris(N-phenyl-1-naphthylamino)-1,3,5-triazine;-   4,4′,6,6′-tetraphenyl-2,2′-bi-1,3,5-triazine;-   2,4,6-tris([1,1′:3′,1″-terphenyl]-5′-yl)-1,3,5-triazine.

In addition, any of the metal chelated oxinoid compounds includingchelates of oxine itself (also commonly referred to as 8-quinolinol or8-hydroxyquinoline) of Formula (O) useful as host materials in a LEL arealso suitable for use in the ETL.

Some metal chelated oxinoid compounds having high triplet energy can beparticularly useful as an electron-transporting materials. Particularlyuseful aluminum or gallium complex host materials with high tripletenergy levels are represented by Formula (V).

In Formula (V), M₁ represents Al or Ga. R₂-R₇ represent hydrogen or anindependently selected substituent. Desirably, R₂ represents anelectron-donating group. Suitably, R₃ and R₄ each independentlyrepresent hydrogen or an electron donating substituent. A preferredelectron-donating group is alkyl such as methyl. Preferably, R₅, R₅, andR₇ each independently represent hydrogen or an electron-accepting group.Adjacent substituents, R₂-R₇, may combine to form a ring group. L is anaromatic moiety linked to the aluminum by oxygen, which may besubstituted with substituent groups such that L has from 6 to 30 carbonatoms.

Illustrative of useful chelated oxinoid compounds for use in the ETL isAluminum(III) bis(2-methyl-8-hydroxyquinoline)-4-phenylphenolate [alias,Balq].

The same anthracene derivatives according to formula (P) useful as hostmaterials in the LEL can also be used in the ETL.

The thickness of the ETL is in the range of from 5 nm to 200 nm,preferably, in the range of from 10 nm to 150 nm.

Electron Injection Layer

The organic lithium compound of the invention is typically located inthe EIL 138. The EIL may be composed only of the organic lithiumcompound, which is preferred, or there may be other materials present.For example, the EIL may be an n-type doped layer containing at leastone electron-transporting material as a host and at least one n-typedopant. The dopant is capable of reducing the host by charge transfer.The term “n-type doped layer” means that this layer has semiconductingproperties after doping, and the electrical current through this layeris substantially carried by the electrons.

The host in the EIL may be an electron-transporting material capable ofsupporting electron injection and electron transport. Theelectron-transporting material can be selected from theelectron-transporting materials for use in the ETL region as definedabove.

The n-type dopant in the n-type doped EIL may be is selected from alkalimetals, alkali metal compounds, alkaline earth metals, or alkaline earthmetal compounds, or combinations thereof. The term “metal compounds”includes organometallic complexes, metal-organic salts, and inorganicsalts, oxides and halides. Among the class of metal-containing n-typedopants, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, La, Ce, Sm, Eu, Th, Dy, orYb, and their compounds, are particularly useful. The materials used asthe n-type dopants in the n-type doped EIL also include organic reducingagents with strong electron-donating properties. By “strongelectron-donating properties” it is meant that the organic dopant shouldbe able to donate at least some electronic charge to the host to form acharge-transfer complex with the host. Nonlimiting examples of organicmolecules include bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF),tetrathiafulvalene (TTF), and their derivatives. In the case ofpolymeric hosts, the dopant is any of the above or also a materialmolecularly dispersed or copolymerized with the host as a minorcomponent. Preferably, the n-type dopant in the n-type doped EILincludes Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, La, Ce, Nd, Sm, Eu, Tb, Dy,or Yb, or combinations thereof. The n-type doped concentration ispreferably in the range of 0.01-20% by volume of this layer.

When the EIL is composed only of the organic lithium compound of theinvention, the thickness of the EIL is typically less Man 20 nm, andpreferably in the range of less than 5 nm. When an n-type doped EIL isemployed, the thickness is typically less than 200 nm, and preferably inthe range of less than 150 nm.

Cathode

When light emission is viewed solely through the anode, the cathode 140includes nearly any conductive material. Desirable materials haveeffective film-forming properties to ensure effective contact with theunderlying organic layer, promote electron injection at low voltage, andhave effective stability. Useful cathode materials often contain a lowwork function metal (<4.0 eV) or metal alloy. One preferred cathodematerial includes a Mg:Ag alloy as described in U.S. Pat. No. 4,885,221.Another suitable class of cathode materials includes bilayers includinga thin inorganic EIL in contact with an organic layer (e.g., organic EILor ETL), which is capped with a thicker layer of a conductive metal.Here, the inorganic EIL preferably includes a low work function metal ormetal salt and, if so, the thicker capping layer does not need to have alow work function. One such cathode includes a thin layer of LiFfollowed by a thicker layer of Al as described in U.S. Pat. No.5,677,572. Other useful cathode material sets include, but are notlimited to, those disclosed in U.S. Pat. Nos. 5,059,861, 5,059,862, and6,140,763.

When light emission is viewed through the cathode, cathode 140 should betransparent or nearly transparent. For such applications, metals shouldbe thin or one should use transparent conductive oxides, or includethese materials. Optically transparent cathodes have been described inmore detail in U.S. Pat. Nos. 4,885,211, 5,247,190, 5,703,436,5,608,287, 5,837,391, 5,677,572, 5,776,622, 5,776,623, 5,714,838,5,969,474, 5,739,545, 5,981,306, 6,137,223, 6,140,763, 6,172,459,6,278,236, 6,284,393, and EP 1 076 368. Cathode materials are typicallydeposited by thermal evaporation, electron beam evaporation, ionsputtering, or chemical vapor deposition. When needed, patterning isachieved through many well known methods including, but not limited to,through-mask deposition, integral shadow masking, for example asdescribed in U.S. Pat. No. 5,276,380 and EP 0 732 868, laser ablation,and selective chemical vapor deposition.

Substrate

OLED 100 is typically provided over a supporting substrate 110 whereeither the anode 120 or cathode 140 can be in contact with thesubstrate. The electrode in contact with the substrate is convenientlyreferred to as the bottom electrode. Conventionally, the bottomelectrode is the anode 120, but this invention is not limited to thatconfiguration. The substrate can either be light transmissive or opaque,depending on the intended direction of light emission. The lighttransmissive property is desirable for viewing the EL emission throughthe substrate. Transparent glass or plastic is commonly employed in suchcases. The substrate can be a complex structure comprising multiplelayers of materials. This is typically the case for active matrixsubstrates wherein TFTs are provided below the OLED layers. It is stillnecessary that the substrate, at least in the emissive pixelated areas,be comprised of largely transparent materials such as glass or polymers.For applications where the EL emission is viewed through the topelectrode, the transmissive characteristic of the bottom support isimmaterial, and therefore the substrate can be light transmissive, lightabsorbing or light reflective. Substrates for use in this case include,but are not limited to, glass, plastic, semiconductor materials such assilicon, ceramics, and circuit board materials. Again, the substrate canbe a complex structure comprising multiple layers of materials such asfound in active matrix TFT designs. It is necessary to provide in thesedevice configurations a light-transparent top electrode.

Deposition of Organic Layers

The organic materials mentioned above are suitably deposited throughsublimation, but can be deposited from a solvent with an optional binderto improve film formation. If the material is a polymer, solventdeposition is usually preferred. The material to be deposited bysublimation can be vaporized from a sublimator “boat” often comprised ofa tantalum material, e.g., as described in U.S. Pat. No. 6,237,529, orcan be first coated onto a donor sheet and then sublimed in closerproximity to the substrate. Layers with a mixture of materials canutilize separate sublimator boats or the materials can be pre-mixed andcoated from a single boat or donor sheet. Patterned deposition can beachieved using shadow masks, integral shadow masks (U.S. Pat. No.5,294,870), spatially-defined thermal dye transfer from a donor sheet(U.S. Pat. No. 5,851,709 and U.S. Pat. No. 6,066,357) and inkjet method(U.S. Pat. No. 6,066,357).

Organic materials useful in making OLEDs, for example organichole-transporting materials, organic light-emitting materials doped withan organic electroluminescent components have relatively complexmolecular structures with relatively weak molecular bonding forces, sothat care must be taken to avoid decomposition of the organicmaterial(s) during physical vapor deposition. The aforementioned organicmaterials are synthesized to a relatively high degree of purity, and areprovided in the form of powders, flakes, or granules. Such powders orflakes have been used heretofore for placement into a physical vapordeposition source wherein heat is applied for forming a vapor bysublimation or vaporization of the organic material, the vaporcondensing on a substrate to provide an organic layer thereon.

Several problems have been observed in using organic powders, flakes, orgranules in physical vapor deposition: These powders, flakes, orgranules are difficult to handle. These organic materials generally havea relatively low physical density and undesirably low thermalconductivity, particularly when placed in a physical vapor depositionsource which is disposed in a chamber evacuated to a reduced pressure aslow as 10⁻⁶ Torr. Consequently, powder particles, flakes, or granulesare heated only by radiative heating from a heated source, and byconductive heating of particles or flakes directly in contact withheated surfaces of the source. Powder particles, flakes, or granuleswhich are not in contact with heated surfaces of the source are noteffectively heated by conductive heating due to a relatively lowparticle-to-particle contact area; This can lead to nonuniform heatingof such organic materials in physical vapor deposition sources.Therefore, result in potentially nonuniform vapor-deposited organiclayers formed on a substrate.

These organic powders can be consolidated into a solid pellet. Thesesolid pellets consolidating into a solid pellet from a mixture of asublimable organic material powder are easier to handle. Consolidationof organic powder into a solid pellet can be accomplished withrelatively simple tools. A solid pellet formed from mixture comprisingone or more non-luminescent organic non-electroluminescent componentmaterials or luminescent electroluminescent component materials ormixture of non-electroluminescent component and electroluminescentcomponent materials can be placed into a physical vapor depositionsource for making organic layer. Such consolidated pellets can be usedin a physical vapor deposition apparatus.

In one aspect, the present invention provides a method of making anorganic layer from compacted pellets of organic materials on asubstrate, which will form part of an OLED.

One preferred method for depositing the materials of the presentinvention is described in US 2004/0255857 (patented as U.S. Pat. No.7,611,587 on Nov. 3, 2009) and U.S. Ser. No. 10/945,941 (patented asU.S. Pat. No. 7,288,286 on Oct. 30, 2007) where different sourceevaporators are used to evaporate each of the materials of the presentinvention. A second preferred method involves the use of flashevaporation where materials are metered along a material feed path inwhich the material feed path is temperature controlled. Such a preferredmethod is described in the following co-assigned patent applications:U.S. Ser. No. 10/784,585 (patented as U.S. Pat. No. 7,232,588 on Jun.19, 2007); U.S. Ser. No. 10/805,980 (patented as U.S. Pat. No. 7,238,389on Jul. 3, 2007); U.S. Ser. No. 10/945,940 (patented as U.S. Pat. No.7,288,285 on Oct. 30, 2007); U.S. Ser. No. 10/945,941 (patented as U.S.Pat. No. 7,288,286 on Oct. 30, 2007); U.S. Ser. No. 11/050,924(patentedas U.S. Pat. No. 7,625,601 on Dec. 1, 2009); and U.S. Ser. No.11/050,934 (patented as U.S. Pat. No. 7,165,340 on Jan. 23, 2007). Usingthis second method, each material may be evaporated using differentsource evaporators or the solid materials may be mixed prior toevaporation using the same source evaporator.

Encapsulation

Most OLED devices are sensitive to moisture and/or oxygen so they arecommonly sealed in an inert atmosphere such as nitrogen or argon, alongwith a desiccant such as alumina, bauxite, calcium sulfate, clays,silica gel, zeolites, alkaline metal oxides, alkaline earth metaloxides, sulfates, or metal halides and perchlorates. Methods forencapsulation and desiccation include, but are not limited to, thosedescribed in U.S. Pat. No. 6,226,890.

OLED Device Design Criteria

For full color display, the pixelation of LELs can be needed. Thispixelated deposition of LELs is achieved using shadow masks, integralshadow masks, U.S. Pat. No. 5,294,870, spatially defined thermal dyetransfer from a donor sheet, U.S. Pat. Nos. 5,688,551, 5,851,709, and6,066,357, and inkjet method, U.S. Pat. No. 6,066,357.

OLED devices of this invention can employ various well-known opticaleffects in order to enhance its properties if desired. This includesoptimizing layer thicknesses to yield maximum light transmission,providing dielectric mirror structures, providing reflective layers ormicrocavity structures, replacing reflective electrodes withlight-absorbing electrodes, providing anti-glare or anti-reflectioncoatings over the display, providing a polarizing medium over thedisplay, or providing colored, neutral density, or color-conversionfilters over the display. Filters, polarizers, and anti-glare oranti-reflection coatings may be specifically provided over the cover oras part of the cover.

Embodiments of the invention may provide EL devices that have goodluminance efficiency, good operational stability, and reduced drivevoltages. Embodiments of the invention may also give reduced voltagerises over the lifetime of the devices and can be produced with highreproducibility and consistently to provide good light efficiency. Theymay have lower power consumption requirements and, when used with abattery, provide longer battery lifetimes.

EXPERIMENTAL EXAMPLES

It should be understood that in the synthesis of organic molecules,particular synthetic pathways can give rise to molecules, eitherexclusively or as mixtures of molecules, which have the same molecularformulae but differ only in having a particular substituent located at adifferent site somewhere in the molecule. In other words, the moleculesor the molecules in the mixtures may differ from each other by thearrangement of their substituents or more generally, the arrangement ofsome of their atoms in space. When this occurs, the materials arereferred to as isomers. A broader definition of an isomer can be foundin Grant and Hackh's Chemical Dictionary, Fifth Edition, McGraw-HillBook Company, page 313. The synthetic pathway outlined for Example 2 isan example of a pathway that can give rise to isomers by virtue of howthe acetylene molecule reacts spatially with the unsymmetrical frameworkof the 8H-cyclopent[a]acenaphthylen-8-one entity of the second molecule.In this particular example, two isomers are possible, ETM2 and ETM7. Itshould be realized that the current invention includes not only examplesof molecules represented by generic Formulae I, II and III and theirspecific molecular examples, but also includes all the isomersassociated with these structures. In addition, examples of compounds ofthe invention and their isomers are not limited to those derived from asymmetrical or unsymmetrical 8H-cyclopent[a]acenaphthylen-8-oneframework, but can also include other frameworks and methods ofpreparation that are useful in producing compounds of Formulae I, II andIII.

Example 1

Inventive Compound, ETM1 was synthesized as outlined in the followingscheme:

7,9-Diphenyl-8H-Cyclopent[a]acenaphthylen-8-one (1)

7,9-Diphenyl-8H-Cyclopent[a]acenaphthylen-8-one, (aka Acecyclone), (1)was prepared according to the procedure of W. Dilthey, I ter Horst andW. Schommer; Journal fuer Praktische Chemie (Leipzig), 143, (1935),189-210, in satisfactory yield.

8-[1,1′-Biphenyl]-4-yl-7,10-diphenylfluoranthene (ETM1)

Acecyclone (12 g, 33.6 mMole) and 4-biphenylacetylene (9.0 g, 50.5mMole) were heated to gentle reflux in ortho-dichlorobenzene (100 mL)for 2 hours. The reaction was then cooled, treated with methanol (20 mL)and stirred at room temperature for 1 hour. The resulting yellow solidwas filtered off, washed well with methanol and dried. Yield of productETM1, 17.4 g. Before use in device fabrication, ETM1 was sublimed at220° C./10⁻³ mm Hg.

Example 2

The inventive compound ETM2 was synthesized as outlined in the followingscheme:

5-Bromoacenaphthenequinone (2)

5-Bromoacenaphthenequinone (2) was prepared according to the procedureof Gordon H. Rule and Samuel B. Thompson; Journal of the ChemicalSociety, (1937), 1761-1763, in satisfactory yield.

3-Bromo-7,9-diphenyl-8H-Cyclopent[a]acenaphthylen-8-one (3)

1,3-Diphenylacetone (17.5 g, 83 mMole) was dissolved in methanol (240mL) and heated to 65° C. To the solution was added5-bromoacenaphthenequinone (2), (20 g, 75 mMole). The resultingwell-stirred suspension was then treated with 1M-methanolic KOH (100 mL,100 mMole) at a fast drip rate, whereupon the dark colored productprecipitated immediately. The mixture was then stirred at 65° C. for 1hour, cooled and filtered. The black solid was washed well withmethanol, ether and dried. Yield of product (3), (31 g).

3-Bromo-8-[1,1′-biphenyl]-4-yl-7,10-diphenylfluoranthene (4)

A mixture of 3-bromo-7,9-diphenyl-8H-Cyclopent[a]acenaphthylen-8-one,(20 g, 46 mMole) and 4-biphenylacetylene (12.3 g, 69 mMole) inortho-dichlorobenzene (200 mL) were heated to gentle reflux for 2 hours.The resulting solution was cooled and treated with methanol (150 mL).During the course of 1 hour the product crystallized as a bright yellowsolid. Yield of product (4), 22 g.

8-[1,1′-Biphenyl]-4-yl-3,7,10-triphenylfluoranthene (ETM2)

A mixture of 3-bromo-8-[1,1′-biphenyl]-4-yl-7,10-diphenylfluoranthene(7.2 g, 12 mMole), tetrakis(triphenylphosphine)palladium(0) (0.44 g,3-mol-% based on the fluoranthene) and phenylboronic acid (1.8 g, 14mMole), were suspended in toluene (100 mL) and stirred well with amechanical stirrer. To this was then added 2M-Na₂CO₃ (14 mL) followed byethanol (20 mL) and the mixture heated to gentle reflux for 1 hour. Thismixture was then cooled to room temperature and treated with methanol(100 mL). The yellow solid was filtered off, washed well with water,methanol and ether, and then dried. Yield of product ETM2, 5.1 g. Beforeuse in device fabrication, ETM2 was sublimed at 260° C./10⁻³ mm Hg.

Example 3 Preparation of Devices 3.1 through 3.14

A series of EL devices (3.1 through 3.14) were constructed in thefollowing manner:

1. A glass substrate coated with an 85 nm layer of indium-tin oxide(ITO), as the anode, was sequentially ultrasonicated in a commercialdetergent, rinsed in deionized water and exposed to oxygen plasma forabout 1 min.

2. Over the ITO was deposited a 1 nm fluorocarbon (CFx) hole-injectinglayer (HIL) by plasma-assisted deposition of CHF₃ as described in U.S.Pat. No. 6,208,075.

3. Next a layer of hole-transporting material4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) was deposited to athickness of 95 nm.

4. A 20 nm light-emitting layer (LEL) of composition as indicated inTable 1 of host material P-4, dopant and dopant % by volume, was thendeposited.

5. A 35 nm electron-transporting layer (ETL) as shown in Table 1, wasvacuum-deposited over the LEL.

6. An electron-injecting layer (EIL) as shown in Table 1, was vacuumdeposited onto the ETL. When LiF was used, the thickness was 0.5 nm; fororganic alkali metal compounds, the thickness was 3.5 nm

7 And finally, a 100 nm layer of aluminum was deposited onto the EIL, toform the cathode.

The above sequence completes the deposition of the EL device. The devicewas then hermetically packaged in a dry glove box for protection againstambient environment.

The devices thus formed were tested for luminous efficiency at anoperating current of 20 mA/cm² and the results are reported in Table 1.Structures of comparative fluoranthenes are shown below.

TABLE 1

Comp-1

Comp-2 Device Results Drive Example Volt. Efficiency (Type) LEL ETL EIL(Volts) (cd/A) 3.1 P-4 + 2% ETM2 LiF 7.2 3.1 (Compar- ETM2 ative) 3.2P-4 + 6% ETM2 LiF 6.6 4.6 (Compar- ETM2 ative) 3.3 P-4 + 10% ETM2 LiF7.1 4.3 (Compar- ETM2 ative) 3.4 P-4 + 5% Comp-1 EIM1 7.3 0.7 (Compar-Comp-1 ative) 3.5 P-4 + 7% Comp-1 EIM1 7.1 0.7 (Compar- Comp-1 ative)3.6 P-4 + 9% Comp-1 EIM1 7.1 0.7 (Compar- Comp-1 ative) 3.7 P-4 + 10%P-1 LiF 9.3 1.5 (Compar- Comp-2 ative) 3.8 P-4 + 10% 50% P-1 + LiF 4.74.9 (Compar- Comp-2 50% EIM2 ative) 3.9 P-4 + 7% Comp-2 EIM1 5.6 3.4(Compar- Comp-2 ative) 3.10 P-4 + 7% Comp-2 + EIM1 5.6 3.0 (Compar-Comp-2 50% EIM2 ative) 3.11 P-4 + 7% ETM2 EIM1 4.2 11.4 (Inven- ETM2tive) 3.12 P-4 + 9% ETM2 EIM1 4.2 11.0 (Inven- ETM2 tive) 3.13 P-4 + 7%80% ETM2 + EIM1 4.4 9.6 (Inven- ETM2 20% EIM2 tive) 3.14 P-4 + 9% 80%ETM2 + EIM1 4.4 9.8 (Inven- ETM2 20% EIM2 tive)

Comparative devices 3.1 to 3.3 of Table 1 use the materials of theinvention in both the LEL and ETL. The organolithium complex as requiredby the invention, is omitted as the EIL and replaced with LiF. Thesedevices with LiF show high voltage and low luminance efficiency,indicating that LiF is not a satisfactory material for the EIL.Comparative devices 3.4 to 3.6 with comparative material Comp-1 employthe organolithium complex of the invention in the EIL. Comp-1, whichfalls outside the scope of the current invention, is present as both alight-emitting material in the LEL and as the material of the ETL. Theresults in Table 1 for devices 3.4 to 3.6 show high voltage and lowluminance indicating that using the organolithium complex in the EIL isnot sufficient for good performance and that the choice of material tobe used in the LEL and ETL is also important.

Devices 3.7 and 3.8 use a second comparative material Comp-2. Even whencombined with state-of-the-art ETLs and either LiF or EIM1 as the EILs,these devices also show very poor performances. Furthermore, in devices3.7 and 3.10 when Comp-2 is in both the LEL and ETL with EIM1 as theEIL, performances are still low. Materials with a fluoranthene structurewith annulated rings such as Comp-1 and Comp-2 are not useful.

In the inventive devices 3.11 to 3.14 where the inventive compound ETM2is present in both the LEL and the ETL with the organolithium complexEIM1 as the EIL, the highly desirable low drive voltages and highluminance efficiency performance is superior to the comparisons.

These experiments demonstrate surprising and unexpected synergisticresults between the use of certain fluoranthene structures in the LELand organic lithium materials in the EIL.

Example 4 Preparation of Devices 4.1 through 4.6

A series of EL devices (4.1 through 4.6) were constructed in a similarmanner to Example 3, except that ETM2 was used at a 10% level in the LELof step 4, and EIM2 was mixed with ETM2 in the ETL layer of step 5, asshown in Table 2. The results are reported in Table 2.

TABLE 2 Device Results Drive Example Volt. Efficiency (Type) LEL ETL EIL(Volts) (cd/A) 4.1 P-4 + 10% ETM2 EIM1 4.1 10.5 (Inventive) ETM2 4.2P-4 + 10% ETM2 + 5% EIM1 4.3 10.6 (Inventive) ETM2 EIM2 4.3 P-4 + 10%ETM2 + 10% EIM1 4.4 10.6 (Inventive) ETM2 EIM2 4.4 P-4 + 10% ETM2 + 20%EIM1 4.4 10.4 (Inventive) ETM2 EIM2 4.5 P-4 + 10% ETM2 + 30% EIM1 4.510.4 (Inventive) ETM2 EIM2 4.6 P-4 + 10% ETM2 + 50% EIM1 4.7 10.1(Inventive) ETM2 EIM2

From Table 2 it can be seen that material EIM2 can be mixed with ETM2 inthe ETL without a detrimental effect on drive voltage or luminanceefficiency performances. The ability to be able to mix materials in theETL with no loss of performance is very important. Table 3 shows thetime in hours, it takes to reach a luminance efficiency of 50% of theoriginal value when the devices are subjected to a current density of 80mA/cm². As can be seen from this table, mixing EIM2 into the ETL withETM2 at various levels leads to improved fade performance.

TABLE 3 Stability of Devices Example T₅₀ ^(@) 80 mA/cm² (Type) ETL(hours) 4.1 ETM2 126 (Inventive) 4.3 ETM2 + 10% 157 (Inventive) EIM2 4.5ETM2 + 30% 158 (Inventive) EIM2

Example 5 Preparation of Devices 5.1 through 5.6

A series of EL devices (5.1 through 5.6) was constructed in a similarmanner to Example 3, except that P-2 was used in place of P-4 and ETM2was used at a 10% level in the LEL layer of step 4. Also, a mixture ofETM2 and EIM1, as indicated in Table 4, was used in the ETL of step 5.The results are reported in Tables 4 and 5.

TABLE 4 Device Results Drive Example Volt. Efficiency (Type) LEL ETL EIL(Volts) (cd/A) 5.1 P-2 + 10% ETM2 EIM1 4.2 10.3 (Inventive) ETM2 5.2P-2 + 10% ETM2 + 5% EIM1 4.3 10.3 (Inventive) ETM2 EIM2 5.3 P-2 + 10%ETM2 + 10% EIM1 4.2 9.9 (Inventive) ETM2 EIM2 5.4 P-2 + 10% ETM2 + 20%EIM1 4.4 10.0 (Inventive) ETM2 EIM2 5.5 P-2 + 10% ETM2 + 30% ETM1 4.49.0 (Inventive) ETM2 EIM2 5.6 P-2 + 10% ETM2 + 50% EIM1 4.6 8.1(Inventive) ETM2 EIM2

Table 4 shows that the advantages of the current invention are notlimited to the blue host material P-4. In devices 5.1 through 5.6 theblue host P-2 has been used with similar results in terms of low drivevoltages and high luminance efficiencies to those shown for P-4 inExample 4. In addition, Table 5 shows the advantages of mixing EIM2 inthe ETL with ETM2. As the amount of EIM2 is increased the T₅₀ fade valueincreases indicating improved fade performance.

TABLE 5 Stability of Devices Example T₅₀ ^(@) 80 mA/cm² (Type) ETL(hours) 5.1 ETM2 115 (Inventive) 5.3 ETM2 + 10% 140 (Inventive) EIM2 5.4ETM2 + 20% 157 (Inventive) EIM2 5.5 ETM2 + 30% 185 (Inventive) EIM2 5.6ETM2 + 50% 218 (Inventive) EIM2

Example 6 Preparation of Devices 6.1 through 6.6

A series of EL devices (6.1 through 6.6) was constructed in a similarmanner to Example 3, except that ETM9 was used instead of ETM2, at a 10%level in the LEL layer of step 4. Also, a mixture of ETM2 and EIM1, asindicated in Table 6, was used in the ETL of step 5. The results arereported in Tables 6 and 7.

TABLE 6 Device Results Drive Example Volt. Efficiency (Type) LEL ETL EIL(Volts) (cd/A) 6.1 P-4 + 10% ETM2 EIM1 5.0 9.2 (Inventive) ETM9 6.2P-4 + 10% ETM2 + 5% EIM1 5.0 8.9 (Inventive) ETM9 EIM2 6.3 P-4 + 10%ETM2 + 10% EIM1 4.9 8.9 (Inventive) ETM9 EIM2 6.4 P-4 + 10% ETM2 + 20%EIM1 4.8 8.7 (Inventive) ETM9 EIM2 6.5 P-4 + 10% ETM2 + 30% EIM1 4.9 8.6(Inventive) ETM9 EIM2 6.6 P-4 + 10% ETM2 + 50% EIM1 4.9 8.2 (Inventive)ETM9 EIM2

Table 6 shows that the advantages of the current invention with ETM9. Indevices 6.1 through 6.6, ETM9 has been used with similar results interms of low drive voltages and high luminance efficiencies to thoseshown for EIM2 in Example 4. In addition, Table 7 again shows theadvantages of mixing EIM2 in the ETL with ETM9. As the amount of EIM2 isincreased the T₅₀ fade value increases indicating improved fadeperformance.

TABLE 7 Device Stability Example T₅₀ ^(@) 80 mA/cm² (Type) ETL (hours)6.1 ETM9 103 (Inventive) 6.4 ETM9 + 20% 128 (Inventive) EIM2 6.5 ETM9 +30% 136 (Inventive) EIM2 6.6 ETM9 + 50% 150 (Inventive) EIM2

Example 7 Preparation of Devices 7.1 through 7.6

A series of EL devices (7.1 through 7.6) was constructed in a similarmanner to Example 3, except that ETM6 was used instead of ETM2, at a 10%level in the LEL layer of step 4. Also, a mixture of ETM6 and EIM1, asindicated in Table 8, was used in the ETL of step 5. The results arereported in Tables 8 and 9.

TABLE 8 Device Results Drive Example Volt. Efficiency (Type) LEL ETL EIL(Volts) (cd/A) 7.1 P-4 + 10% ETM6 EIM1 4.7 12.3 (Inventive) ETM6 7.2P-4 + 10% ETM6 + 5% EIM1 4.3 12.2 (Inventive) ETM6 EIM2 7.3 P-4 + 10%ETM6 + 10% EIM1 4.5 11.6 (Inventive) ETM6 EIM2 7.4 P-4 + 10% ETM6 + 20%EIM1 4.6 11.4 (Inventive) ETM6 EIM2 7.5 P-4 + 10% ETM6 + 30% EIM1 4.511.3 (Inventive) ETM6 EIM2 7.6 P-4 + 10% ETM6 + 50% EIM1 4.7 10.9(Inventive) ETM6 EIM2

Table 6 shows that the advantages of the current invention with ETM6. Indevices 7.1 through 7.6, ETM6 has been used with similar results interms of low drive voltages and high luminance efficiencies to thoseshown for ETM2 in Example 4. In addition, Table 9 again shows theadvantages of mixing EIM2 in the ETL with ETM6. As the amount of EIM2 isincreased the T₅₀ fade value increases indicating improved fadeperformance.

TABLE 9 Device Stability Example T₅₀ ^(@) 80 mA/cm² (Type) ETL (hours)7.1 ETM6 286 (Inventive) 7.5 ETM6 + 30% 308 (Inventive) EIM2 7.6 ETM6 +50% 292 (Inventive) EIM2

The invention has been described in detail with particular reference tocertain preferred embodiments thereof but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention. The patents and other publications referred to areincorporated herein in their entirety.

PARTS LIST

100 OLED 110 Substrate 120 Anode 130 Hole-Injecting layer (HIL) 132Hole-Transporting layer (HTL) 134 Light-Emitting layer (LEL) 135Hole-Blocking Layer (HBL) 136 Electron-Transporting layer (ETL) 138Electron-Injecting layer (EIL) 140 Cathode 150 Voltage/Current Source160 Electrical Connectors

The invention claimed is:
 1. An OLED device comprising a cathode, ananode, and having therebetween a light emitting layer, anelectron-transporting layer and an electron-injecting layer, (a) thelight emitting layer containing a host and up to 50 volume % of alight-emitting fluoranthene compound with a 7,10-diaryl substitutedfluoranthene nucleus having no aromatic rings annulated to thefluoranthene nucleus; (b) the electron-injecting layer being locatedbetween the cathode and the light-emitting layer and containing anorganic lithium compound, and (c) the electron-transporting layerlocated between the electron-injecting layer and the light-emittinglayer and containing a fluoranthene compound with a 7,10-diarylsubstituted fluoranthene nucleus having no aromatic rings annulated tothe fluoranthene nucleus, wherein each of the fluoranthene compound inthe light emitting layer and the electron-transporting layer isaccording to Formula (III-a) or Formula (III-b):

wherein: R₂ and R₄ are independently hydrogen or an aromatic groupcontaining 6 to 24 carbon atoms with the proviso that R₂ and R₄ cannotboth be hydrogen nor can R₂ be joined with R to form a ring; R ishydrogen or an optional substituent; and n and m in Formula (III-a) orFormula (III-b) are independently 1-5, and wherein the organic lithiumcompound is according to Formula (V):

wherein: Z and the dashed arc represent two to four atoms and the bondsnecessary to complete a 5- to 7-membered ring with the lithium cation;each A represents hydrogen or a substituent and each B representshydrogen or an independently selected substituent on the Z atoms,provided that two or more substituents may combine to form a fused ringor a fused ring system; j is 0-3 and k is 1 or 2; and m and n in Formula(V) are independently selected integers selected to provide a neutralcharge on the complex.
 2. The OLED device of claim 1 wherein the A and Bsubstituents of Formula (V) together form an additional ring system. 3.The OLED device of claim 2 wherein the ring formed between the A and Bsubstituents contains at least one heteroatom in addition to thenitrogen that is attached to A.
 4. The OLED device of claim 1 whereinthe organic lithium compound is chosen from:


5. The OLED device of claim 1 wherein the host in the light-emittinglayer is a polycyclic aromatic hydrocarbon.
 6. The OLED device of claim5 wherein the polycyclic aromatic hydrocarbon is an anthracene accordingto Formula (P):

wherein: R₁-R₁₀ are independently chosen from hydrogen, alkyl groupsfrom 1-24 carbon atoms or aromatic groups from 1-24 carbon atoms.
 7. TheOLED device of claim 1 wherein the electron-transporting layeradditionally includes an alkali metal compound.
 8. The OLED device ofclaim 7 wherein the alkali metal compound is an organic lithium compoundaccording to Formula (V):

wherein: Z and the dashed arc represent two to four atoms and the bondsnecessary to complete a 5- to 7-membered ring with the lithium cation;each A represents hydrogen or a substituent and each B representshydrogen or an independently selected substituent on the Z atoms,provided that two or more substituents may combine to form a fused ringor a fused ring system; and j is 0-3 and k is 1 or 2; and m and n areindependently selected integers selected to provide a neutral charge onthe complex.
 9. A method of emitting light comprising applying anelectric potential across the device of claim
 1. 10. A displaycomprising the device of claim 1.